Acoustic wave device

ABSTRACT

An acoustic wave device includes a piezoelectric body portion, an interdigital transducer electrode connected to a first terminal and a second terminal, and a reflector connected to the second terminal. In the interdigital transducer electrode, in the interdigital transducer electrode, where, of a group of electrode fingers, the electrode finger located at one end in a second direction is a first end electrode finger and the electrode finger located at another end is a second end electrode finger, the first end electrode finger is located between the reflector and the second end electrode finger in the second direction. An outer busbar portion of one of a first busbar and a second busbar, not connected to the first end electrode finger, is located on an inner side in the second direction relative to a center portion, in a first direction, of the first end electrode finger.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese PatentApplication No. 2017-242526 filed on Dec. 19, 2017 and is a ContinuationApplication of PCT Application No. PCT/JP2018/039061 filed on Oct. 19,2018. The entire contents of each application are hereby incorporatedherein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention generally relates to an acoustic wave device and,more specifically, to an acoustic wave device including an interdigitaltransducer electrode.

2. Description of the Related Art

As an acoustic wave device, there is known an acoustic wave device thatincludes a piezoelectric substrate (piezoelectric body portion) and aninterdigital transducer electrode provided on or above the piezoelectricsubstrate and in which wide portions are provided in part of electrodefingers of the interdigital transducer electrode (see, for example,International Publication No. 2014/192756). In an example of theacoustic wave device described in International Publication No.2014/192756, a reflector is formed on each side of the interdigitaltransducer electrode in a propagation direction of surface acousticwaves on the piezoelectric substrate. The interdigital transducerelectrode and the reflectors include a metal material. The acoustic wavedevice described in International Publication No. 2014/192756 has suchcharacteristics that the acoustic wave device has a structure ofsuppressing a transverse-mode ripple by forming a piston mode in theinterdigital transducer electrode.

In the acoustic wave device described in International Publication No.2014/192756, the interdigital transducer electrode includes a firstbusbar, a second busbar disposed apart from the first busbar, aplurality of first electrode fingers of which proximal ends areelectrically connected to the first busbar and distal ends are have agreater width toward the second busbar, and a plurality of secondelectrode fingers of which proximal ends are connected to the secondbusbar and distal ends are have a greater width toward the first busbar.In the above-described acoustic wave device, wide portions are providedin both of the first electrode fingers and the second electrode fingers.

The first busbar includes a plurality of opening portions separatelydisposed along a length direction of the first busbar. The first busbarincludes an inner busbar portion located closer to the first electrodefingers than the plurality of opening portions and having a greaterwidth in the length direction of the first busbar, a center busbarportion in which the plurality of opening portions is provided, and anouter busbar portion located across the center busbar portion from theinner busbar portion.

The second busbar includes a plurality of opening portions separatelydisposed along a length direction of the second busbar. The secondbusbar includes an inner busbar portion located closer to the secondelectrode fingers than the plurality of opening portions and having agreater width in the length direction of the second busbar, a centerbusbar portion in which the plurality of opening portions is provided,and an outer busbar portion located across the center busbar portionfrom the inner busbar portion.

In the acoustic wave device in which the wide portions are provided in aportion of the electrode fingers of the interdigital transducerelectrode, for example, the outer busbar portions are located adjacentto metal material portions such as reflectors different in potential inend regions of the interdigital transducer electrode in the lengthdirections of the first busbar and second busbar, so a surge breakdownsometimes occurs in the outer busbar portions because of electrostaticdischarge (ESD).

SUMMARY OF THE INVENTION

Preferred embodiments of the present invention provide acoustic wavedevices that are each able to significantly improve ESD tolerance whilesignificantly reducing or preventing interference with a piston mode.

An acoustic wave device according to a preferred embodiment of thepresent invention includes a first terminal, a second terminal, apiezoelectric body portion, an interdigital transducer electrode, and areflector. The second terminal has a lower potential than the firstterminal. The interdigital transducer electrode is provided on or abovethe piezoelectric body portion and electrically connected to the firstterminal and the second terminal. The reflector is provided on or abovethe piezoelectric body portion and electrically connected to the secondterminal. The interdigital transducer electrode includes a first busbar,a second busbar, a plurality of first electrode fingers, and a pluralityof second electrode fingers. The first busbar is electrically connectedto the first terminal. The second busbar is opposed to the first busbarin a first direction and electrically connected to the second terminal.The plurality of first electrode fingers are connected to the firstbusbar and have a greater width from the first busbar toward the secondbusbar in the first direction. The plurality of second electrode fingersare connected to the second busbar and have a greater width from thesecond busbar toward the first busbar in the first direction. Theplurality of first electrode fingers and the plurality of secondelectrode fingers are spaced apart from each other in a second directionperpendicular or substantially perpendicular to the first direction. Atleast one electrode finger of the plurality of first electrode fingersincludes a wide portion having a greater width in the second directionthan a center portion, in the first direction, of the at least oneelectrode finger, and at least one electrode finger of the plurality ofsecond electrode fingers includes a wide portion having a greater widthin the second direction than a center portion, in the first direction,of the at least one electrode finger. Each of the first busbar and thesecond busbar includes an opening portion, an inner busbar portion, anouter busbar portion, and a coupling portion. The inner busbar portionis located closer to the plurality of first electrode fingers and theplurality of second electrode fingers than the opening portion in thefirst direction. The outer busbar portion is located across the openingportion from the inner busbar portion in the first direction. Thecoupling portion couples the inner busbar portion and the outer busbarportion in the first direction. In the interdigital transducerelectrode, where, of a group of electrode fingers including theplurality of first electrode fingers and the plurality of secondelectrode fingers, the electrode finger located at one end in the seconddirection is a first end electrode finger and the electrode fingerlocated at another end is a second end electrode finger, the first endelectrode finger is located between the reflector and the second endelectrode finger in the second direction. The outer busbar portion ofone of the first busbar and the second busbar, not connected to thefirst end electrode finger, is located on an inner side in the seconddirection relative to a center portion, in the first direction, of thefirst end electrode finger.

An acoustic wave device according to a preferred embodiment of thepresent invention includes a first terminal, a second terminal, apiezoelectric body portion, a plurality of interdigital transducerelectrodes, and two reflectors. The second terminal has a lowerpotential than the first terminal. The plurality of interdigitaltransducer electrodes are provided on or above the piezoelectric bodyportion and electrically connected to the first terminal and the secondterminal. The two reflectors are provided on or above the piezoelectricbody portion and reflect acoustic waves excited by the plurality ofinterdigital transducer electrodes. Each of the plurality ofinterdigital transducer electrodes includes a first busbar, a secondbusbar, a plurality of first electrode fingers, and a plurality ofsecond electrode fingers. The second busbar is opposed to the firstbusbar in a first direction. The plurality of first electrode fingersare connected to the first busbar and have a greater width from thefirst busbar toward the second busbar in the first direction. Theplurality of second electrode fingers are connected to the second busbarand have a greater width from the second busbar toward the first busbarin the first direction. The plurality of first electrode fingers and theplurality of second electrode fingers are spaced apart from each otherin a second direction perpendicular or substantially perpendicular tothe first direction. At least one electrode finger of the plurality offirst electrode fingers includes a wide portion having a greater widthin the second direction than a center portion, in the first direction,of the at least one electrode finger, and at least one electrode fingerof the plurality of second electrode fingers includes a wide portionhaving a greater width in the second direction than a center portion, inthe first direction, of the at least one electrode finger. Each of thefirst busbar and the second busbar includes an opening portion, an innerbusbar portion, an outer busbar portion, and a coupling portion. Theinner busbar portion is located closer to the plurality of firstelectrode fingers and the plurality of second electrode fingers than theopening portion in the first direction. The outer busbar portion islocated across the opening portion from the inner busbar portion in thefirst direction. The coupling portion couples the inner busbar portionand the outer busbar portion in the first direction. The plurality ofinterdigital transducer electrodes are provided in the second direction.The two reflectors each are located across the interdigital transducerelectrode at any one of both sides of the plurality of interdigitaltransducer electrodes provided in the second direction from theinterdigital transducer electrode adjacent to the interdigitaltransducer electrode at the any one of both sides. In the interdigitaltransducer electrode adjacent to one of the two reflectors, of theplurality of interdigital transducer electrodes, where, of a group ofelectrode fingers including the plurality of first electrode fingers andthe plurality of second electrode fingers, the electrode finger locatedat one end in the second direction is a first end electrode finger andthe electrode finger located at another end is a second end electrodefinger, the first end electrode finger is located between the one of thetwo reflectors and the second end electrode finger in the seconddirection. In the interdigital transducer electrode adjacent to the oneof the two reflectors, the outer busbar portion of one of the firstbusbar and the second busbar, not connected to the first end electrodefinger, is located on an inner side in the second direction relative toa center portion, in the first direction, of the first end electrodefinger.

An acoustic wave device according to a preferred embodiment of thepresent invention includes a first terminal, a second terminal, apiezoelectric body portion, an interdigital transducer electrode, and areflector. The second terminal has a lower potential than the firstterminal. The interdigital transducer electrode is provided on or abovethe piezoelectric body portion and electrically connected to the firstterminal and the second terminal. The reflector is provided on or abovethe piezoelectric body portion and electrically connected to the secondterminal. The interdigital transducer electrode includes a first busbar,a second busbar, a plurality of first electrode fingers, and a pluralityof second electrode fingers. The first busbar is electrically connectedto the first terminal. The second busbar is opposed to the first busbarin a first direction and electrically connected to the second terminal.The plurality of first electrode fingers are connected to the firstbusbar and have a greater width from the first busbar toward the secondbusbar in the first direction. The plurality of second electrode fingersare connected to the second busbar and have a greater width from thesecond busbar toward the first busbar in the first direction. Theplurality of first electrode fingers and the plurality of secondelectrode fingers are spaced apart from each other in a second directionperpendicular or substantially perpendicular to the first direction. Atleast one electrode finger of the plurality of first electrode fingersincludes a wide portion having a greater width in the second directionthan a center portion, in the first direction, of the at least oneelectrode finger, and at least one electrode finger of the plurality ofsecond electrode fingers includes a wide portion having a greater widthin the second direction than a center portion, in the first direction,of the at least one electrode finger. Each of the first busbar and thesecond busbar includes an opening portion, an inner busbar portion, anouter busbar portion, and a coupling portion. The inner busbar portionis located closer to the plurality of first electrode fingers and theplurality of second electrode fingers than the opening portion in thefirst direction. The outer busbar portion is located across the openingportion from the inner busbar portion in the first direction. Thecoupling portion couples the inner busbar portion and the outer busbarportion in the first direction. In the interdigital transducerelectrode, where, of a group of electrode fingers including theplurality of first electrode fingers and the plurality of secondelectrode fingers, the electrode finger located at one end in the seconddirection is a first end electrode finger and the electrode fingerlocated at another end is a second end electrode finger, the first endelectrode finger is located between the reflector and the second endelectrode finger in the second direction. The outer busbar portion ofone of the first busbar and the second busbar, not connected to thefirst end electrode finger, is located on an inner side in the seconddirection relative to the inner busbar portion of the busbar notconnected to the first end electrode finger.

An acoustic wave device according to a preferred embodiment of thepresent invention includes a first terminal, a second terminal, apiezoelectric body portion, a plurality of interdigital transducerelectrodes, and two reflectors. The second terminal has a lowerpotential than the first terminal. The plurality of interdigitaltransducer electrodes are provided on or above the piezoelectric bodyportion and electrically connected to the first terminal and the secondterminal. The two reflectors are provided on or above the piezoelectricbody portion and reflect acoustic waves excited by the plurality ofinterdigital transducer electrodes. Each of the plurality ofinterdigital transducer electrodes includes a first busbar, a secondbusbar, a plurality of first electrode fingers, and a plurality ofsecond electrode fingers. The second busbar is opposed to the firstbusbar in a first direction. The plurality of first electrode fingersare connected to the first busbar and have a greater width from thefirst busbar toward the second busbar in the first direction. Theplurality of second electrode fingers are connected to the second busbarand have a greater width from the second busbar toward the first busbarin the first direction. The plurality of first electrode fingers and theplurality of second electrode fingers are spaced apart from each otherin a second direction perpendicular or substantially perpendicular tothe first direction. At least one electrode finger of the plurality offirst electrode fingers includes a wide portion having a greater widthin the second direction than a center portion, in the first direction,of the at least one electrode finger, and at least one electrode fingerof the plurality of second electrode fingers includes a wide portionhaving a greater width in the second direction than a center portion, inthe first direction, of the at least one electrode finger. Each of thefirst busbar and the second busbar includes an opening portion, an innerbusbar portion, an outer busbar portion, and a coupling portion. Theinner busbar portion is located closer to the plurality of firstelectrode fingers and the plurality of second electrode fingers than theopening portion in the first direction. The outer busbar portion islocated across the opening portion from the inner busbar portion in thefirst direction. The coupling portion couples the inner busbar portionand the outer busbar portion in the first direction. The plurality ofinterdigital transducer electrodes are provided in the second direction.The two reflectors each are located across the interdigital transducerelectrode at any one of both sides of the plurality of interdigitaltransducer electrodes provided in the second direction from theinterdigital transducer electrode adjacent to the interdigitaltransducer electrode at the any one of both sides. In the interdigitaltransducer electrode adjacent to one of the two reflectors, of theplurality of interdigital transducer electrodes, where, of a group ofelectrode fingers including the plurality of first electrode fingers andthe plurality of second electrode fingers, the electrode finger locatedat one end in the second direction is a first end electrode finger andthe electrode finger located at another end is a second end electrodefinger, the first end electrode finger is located between the one of thetwo reflectors and the second end electrode finger in the seconddirection. In the interdigital transducer electrode adjacent to the oneof the two reflectors, the outer busbar portion of one of the firstbusbar and the second busbar, not connected to the first end electrodefinger, is located on an inner side in the second direction relative tothe inner busbar portion of the busbar not connected to the first endelectrode finger.

An acoustic wave device according to a preferred embodiment of thepresent invention includes a first terminal, a second terminal, apiezoelectric body portion, and a plurality of interdigital transducerelectrodes. The second terminal has a lower potential than the firstterminal. The plurality of interdigital transducer electrodes isprovided on or above the piezoelectric body portion and electricallyconnected to the first terminal and the second terminal. Each of theplurality of interdigital transducer electrodes includes a first busbar,a second busbar, a plurality of first electrode fingers, and a pluralityof second electrode fingers. The second busbar is opposed to the firstbusbar in a first direction. The plurality of first electrode fingersare connected to the first busbar and have a greater width from thefirst busbar toward the second busbar in the first direction. Theplurality of second electrode fingers are connected to the second busbarand have a greater width from the second busbar toward the first busbarin the first direction. The plurality of first electrode fingers and theplurality of second electrode fingers are spaced apart from each otherin a second direction perpendicular or substantially perpendicular tothe first direction. At least one electrode finger of the plurality offirst electrode fingers includes a wide portion having a greater widthin the second direction than a center portion, in the first direction,of the at least one electrode finger, and at least one electrode fingerof the plurality of second electrode fingers includes a wide portionhaving a greater width in the second direction than a center portion, inthe first direction, of the at least one electrode finger. Each of thefirst busbar and the second busbar includes an opening portion, an innerbusbar portion, an outer busbar portion, and a coupling portion. Theinner busbar portion is located closer to the plurality of firstelectrode fingers and the plurality of second electrode fingers than theopening portion in the first direction. The outer busbar portion islocated across the opening portion from the inner busbar portion in thefirst direction. The coupling portion couples the inner busbar portionand the outer busbar portion in the first direction. Where, of theplurality of interdigital transducer electrodes, one of the twointerdigital transducer electrodes adjacent to each other in the seconddirection is a first interdigital transducer electrode and another oneof the two interdigital transducer electrodes is a second interdigitaltransducer electrode, a distance between the outer busbar portion notconnected to, of a group of electrode fingers including the plurality offirst electrode fingers and the plurality of second electrode fingers,the electrode finger closest to the second interdigital transducerelectrode in the first interdigital transducer electrode and the outerbusbar portion not connected to, of a group of electrode fingersincluding the plurality of first electrode fingers and the plurality ofsecond electrode fingers, the electrode finger closest to the firstinterdigital transducer electrode in the second interdigital transducerelectrode is greater than a distance between a center portion of theelectrode finger closest to the second interdigital transducer electrodein the first interdigital transducer electrode and a center portion ofthe electrode finger closest to the first interdigital transducerelectrode in the second interdigital transducer electrode.

An acoustic wave device according to a preferred embodiment of thepresent invention includes a first terminal, a second terminal, apiezoelectric body portion, and a plurality of interdigital transducerelectrodes. The second terminal has a lower potential than the firstterminal. The plurality of interdigital transducer electrodes areprovided on or above the piezoelectric body portion and electricallyconnected to the first terminal and the second terminal. Each of theplurality of interdigital transducer electrodes includes a first busbar,a second busbar, a plurality of first electrode fingers, and a pluralityof second electrode fingers. The second busbar is opposed to the firstbusbar in a first direction. The plurality of first electrode fingersare connected to the first busbar and have a greater width from thefirst busbar toward the second busbar in the first direction. Theplurality of second electrode fingers are connected to the second busbarand have a greater width from the second busbar toward the first busbarin the first direction. The plurality of first electrode fingers and theplurality of second electrode fingers are spaced apart from each otherin a second direction perpendicular or substantially perpendicular tothe first direction. At least one electrode finger of the plurality offirst electrode fingers includes a wide portion having a greater widthin the second direction than a center portion, in the first direction,of the at least one electrode finger, and at least one electrode fingerof the plurality of second electrode fingers includes a wide portionhaving a greater width in the second direction than a center portion, inthe first direction, of the at least one electrode finger. Each of thefirst busbar and the second busbar includes an opening portion, an innerbusbar portion, an outer busbar portion, and a coupling portion. Theinner busbar portion is located closer to the plurality of firstelectrode fingers and the plurality of second electrode fingers than theopening portion in the first direction. The outer busbar portion islocated across the opening portion from the inner busbar portion in thefirst direction. The coupling portion couples the inner busbar portionand the outer busbar portion in the first direction. Where, of theplurality of interdigital transducer electrodes, one of the twointerdigital transducer electrodes adjacent to each other in the seconddirection is a first interdigital transducer electrode and another oneof the two interdigital transducer electrodes is a second interdigitaltransducer electrode, and where, of a group of electrode fingersincluding the plurality of first electrode fingers and the plurality ofsecond electrode fingers of the first interdigital transducer electrode,the electrode finger located at an end closer to the second interdigitaltransducer electrode in the second direction is a first end electrodefinger of the first interdigital transducer electrode and the electrodefinger located at an end away from the second interdigital transducerelectrode is a second end electrode finger of the first interdigitaltransducer electrode, and, of a group of electrode fingers including theplurality of first electrode fingers and the plurality of secondelectrode fingers of the second interdigital transducer electrode, theelectrode finger located at an end closer to the first interdigitaltransducer electrode in the second direction is a first end electrodefinger of the second interdigital transducer electrode and the electrodefinger located at an end away from the first interdigital transducerelectrode is a second end electrode finger of the second interdigitaltransducer electrode, the first end electrode finger of the firstinterdigital transducer electrode is connected to the first terminal,and the first end electrode finger of the second interdigital transducerelectrode is connected to the second terminal. In each of the firstinterdigital transducer electrode and the second interdigital transducerelectrode, the outer busbar portion electrically connected to one of thefirst terminal and the second terminal, different from the terminal towhich the first end electrode finger is connected, is located on aninner side in the second direction relative to the inner busbar portionelectrically connected to the one of the first terminal and the secondterminal, different from the terminal to which the first end electrodefinger is connected.

An acoustic wave device according to a preferred embodiment of thepresent invention includes a first terminal, a second terminal, apiezoelectric body portion, and a plurality of interdigital transducerelectrodes. The second terminal has a lower potential than the firstterminal. The plurality of interdigital transducer electrodes areprovided on or above the piezoelectric body portion and electricallyconnected to the first terminal and the second terminal. Each of theplurality of interdigital transducer electrodes includes a first busbar,a second busbar, a plurality of first electrode fingers, and a pluralityof second electrode fingers. The second busbar is opposed to the firstbusbar in a first direction. The plurality of first electrode fingersare connected to the first busbar and have a greater width from thefirst busbar toward the second busbar in the first direction. Theplurality of second electrode fingers are connected to the second busbarand have a greater width from the second busbar toward the first busbarin the first direction. The plurality of first electrode fingers and theplurality of second electrode fingers are spaced apart from each otherin a second direction perpendicular or substantially perpendicular tothe first direction. At least one electrode finger of the plurality offirst electrode fingers includes a wide portion having a greater widthin the second direction than a center portion, in the first direction,of the at least one electrode finger, and at least one electrode fingerof the plurality of second electrode fingers includes a wide portionhaving a greater width in the second direction than a center portion, inthe first direction, of the at least one electrode finger. Each of thefirst busbar and the second busbar includes an opening portion, an innerbusbar portion, an outer busbar portion, and a coupling portion. Theinner busbar portion is located closer to the plurality of firstelectrode fingers and the plurality of second electrode fingers than theopening portion in the first direction. The outer busbar portion islocated across the opening portion from the inner busbar portion in thefirst direction. The coupling portion couples the inner busbar portionand the outer busbar portion in the first direction. In at least oneinterdigital transducer electrode of the plurality of interdigitaltransducer electrodes, where, of a group of electrode fingers includingthe plurality of first electrode fingers and the plurality of secondelectrode fingers, the electrode finger located at one end in the seconddirection is a first end electrode finger and the electrode fingerlocated at another end is a second end electrode finger, the first endelectrode finger is located closer to the interdigital transducerelectrode adjacent to the at least one interdigital transducer electrodein the second direction. In the at least one interdigital transducerelectrode, the outer busbar portion of one of the first busbar and thesecond busbar, not connected to the first end electrode finger, islocated on an inner side in the second direction relative to the innerbusbar portion of one of the first busbar and the second busbar, notconnected to the first end electrode finger, at least at a side closerto the adjacent interdigital transducer electrode.

Acoustic wave devices according to preferred embodiments of the presentinvention are each able to significantly improve ESD tolerance whilesignificantly reducing or preventing interference with a piston mode.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of an acoustic wave device according to a firstpreferred embodiment of the present invention.

FIG. 2A is a plan view of a portion of the acoustic wave deviceaccording to the first preferred embodiment of the present invention.FIG. 2B relates to the above acoustic wave device and is across-sectional view taken along the line A-A in FIG. 2A.

FIG. 3 is an enlarged view of a main portion of the above acoustic wavedevice.

FIG. 4 is a view showing a velocity distribution, in a first direction,of an acoustic velocity of acoustic waves that propagate in an acousticwave propagation direction (second direction) in the above acoustic wavedevice.

FIG. 5 is a view showing an electric charge distribution in the aboveacoustic wave device.

FIG. 6 is an enlarged view of a main portion of an acoustic wave deviceaccording to a first modification of the first preferred embodiment ofthe present invention.

FIG. 7 is a plan view of an acoustic wave device according to a secondpreferred embodiment of the present invention.

FIG. 8 is a plan view of a portion of the acoustic wave device accordingto the second preferred embodiment of the present invention.

FIG. 9 relates to the above acoustic wave device and is across-sectional view taken along the line A-A in FIG. 8.

FIG. 10 is an enlarged view of a main portion of the above acoustic wavedevice.

FIG. 11 is a view showing an electric charge distribution in the aboveacoustic wave device.

FIG. 12 is an enlarged view of a main portion of an acoustic wave deviceaccording to a first modification of the second preferred embodiment ofthe present invention.

FIG. 13 is a plan view of a portion of an acoustic wave device accordingto a second modification of the second preferred embodiment of thepresent invention.

FIG. 14 is an enlarged view of a main portion of the above acoustic wavedevice.

FIG. 15 is an enlarged view of a main portion of an acoustic wave deviceaccording to a third modification of the second preferred embodiment ofthe present invention.

FIG. 16 is a cross-sectional view of an acoustic wave device accordingto a fourth modification of the second preferred embodiment of thepresent invention.

FIG. 17 is a cross-sectional view of an acoustic wave device accordingto a fifth modification of the second preferred embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, acoustic wave devices according to preferred embodimentswill be described with reference to the drawings.

FIG. 1 to FIG. 17 that will be used in the following preferredembodiments, and the like, all are representative diagrams, and theratios of the sizes and thicknesses of components in the drawings do notalways reflect actual scale ratios.

First Preferred Embodiment (1.1) Overall Configuration of Acoustic WaveDevice

Hereinafter, an acoustic wave device 1 according to a first preferredembodiment of the present invention will be described with reference tothe drawings.

As shown in FIG. 1, FIG. 2A, FIG. 2B, FIG. 3, and FIG. 4, the acousticwave device 1 according to the first preferred embodiment includes afirst terminal (for example, a signal terminal) 11, second terminals(for example, ground terminals) 12, a piezoelectric body portion 24, aninterdigital transducer (IDT) electrode 3, and reflectors 8. Each secondterminal 12 has a lower potential than the first terminal 11. Therefore,the first terminal 11 has a higher potential than each second terminal12. The first terminal 11 and the second terminals 12 are provided on orabove the piezoelectric body portion 24. Here, the state “provided on orabove the piezoelectric body portion 24” includes the case of beingdirectly provided on the piezoelectric body portion 24 and the case ofbeing indirectly provided on the piezoelectric body portion 24. Theacoustic wave device 1 includes the plurality of (for example, three)second terminals 12. However, the acoustic wave device 1 only needs toinclude at least one second terminal 12. The piezoelectric body portion24 I made of a piezoelectric material. The interdigital transducerelectrode 3 and the reflectors 8 are provided on or above thepiezoelectric body portion 24. Here, the state “provided on or above thepiezoelectric body portion 24” includes the case of being directlyprovided on the piezoelectric body portion 24 and the case of beingindirectly provided on the piezoelectric body portion 24. The acousticwave device 1 according to the first preferred embodiment is asingle-port surface acoustic wave resonator. The acoustic wave device 1includes the two reflectors 8.

The acoustic wave device 1 according to the first preferred embodimentfurther includes a first wiring layer 13 electrically connecting theinterdigital transducer electrode 3 and the first terminal 11 and asecond wiring layer 14 electrically connecting the interdigitaltransducer electrode 3 and the second terminals 12. In FIG. 1, for thesake of convenience of description, the label “H” is assigned to thefirst terminal 11 and portions (high potential portions) electricallyconnected to the first terminal 11 in the interdigital transducerelectrode 3, and the label “E” is assigned to the second terminals 12and portions (low potential portions) electrically connected to thesecond terminals 12 in the interdigital transducer electrode 3. The highpotential portions are different in potential from the low potentialportions. The high potential portions are portions higher in potentialthan the low potential portions. The labels “H”, “E” are not signs andare not actually present. In FIG. 1 and FIG. 2A, dot hatching is appliedto the interdigital transducer electrode 3 and the reflectors 8. Thesehatchings do not represent cross sections and are provided to clearlyshow the relationship among the interdigital transducer electrode 3, thereflectors 8, and the piezoelectric body portion 24. In FIG. 1, dothatching is applied to the first terminal 11, the second terminals 12,the first wiring layer 13, and the second wiring layer 14. Thesehatchings do not represent cross sections and are provided to clearlyshow the relationship among the first terminal 11, the second terminals12, the first wiring layer 13 and the second wiring layer 14, and thepiezoelectric body portion 24.

In the acoustic wave device 1 according to the first preferredembodiment, the piezoelectric body portion 24 is a piezoelectric film,and the above-described interdigital transducer electrode 3 is providedon or above a multilayer board including the piezoelectric body portion24. The multilayer board 2 is a piezoelectric substrate at leastpartially having piezoelectricity.

(1.2) Components of Acoustic Wave Device

Next, the components of the acoustic wave device 1 will be describedwith reference to the drawings.

(1.2.1) Multilayer Board

As shown in FIG. 2B, the multilayer board 2 includes a high acousticvelocity support substrate 21, a low acoustic velocity film 23 directlylaminated on the high acoustic velocity support substrate 21 and throughwhich bulk waves propagate at a lower acoustic velocity than acousticwaves that propagate through the piezoelectric body portion 24, and thepiezoelectric body portion 24 directly laminated on the low acousticvelocity film 23. In the high acoustic velocity support substrate 21,bulk waves propagate at a higher acoustic velocity than acoustic wavesthat propagate through the piezoelectric body portion 24. The lowacoustic velocity film 23 is provided on or above the high acousticvelocity support substrate 21. Here, the state “provided on or above thelow acoustic velocity film 23” includes the case of being directlyprovided on the low acoustic velocity film 23 and the case of beingindirectly provided on the low acoustic velocity film 23. Thepiezoelectric body portion 24 is indirectly laminated on the highacoustic velocity support substrate 21. Accordingly, since the lowacoustic velocity film 23 is located between the high acoustic velocitysupport substrate 21 and the piezoelectric body portion 24 in theacoustic wave device 1, the acoustic velocity of acoustic wavesdecreases. The energy of acoustic waves substantially concentrates in alow acoustic velocity medium. Therefore, with the acoustic wave device1, the effect of enclosing acoustic wave energy into the piezoelectricbody portion 24 and the interdigital transducer electrode 3 in whichacoustic waves are excited is significantly improved. Therefore, withthe acoustic wave device 1, a loss is reduced, and the quality factor isincreased, in comparison with the case where no low acoustic velocityfilm 23 is provided.

The piezoelectric body portion 24 i is preferably made of, for example,lithium tantalate (LiTaO₃), lithium niobate (LiNbO₃), zinc oxide (ZnO),aluminum nitride (AlN), or lead zirconate titanate (PZT).

The high acoustic velocity support substrate 21 supports a multilayerbody including the low acoustic velocity film 23 and the piezoelectricbody portion 24. Here, the high acoustic velocity support substrate 21includes a first main surface 211 and a second main surface 212 that areon opposite sides in the thickness direction. The first main surface 211and the second main surface 212 are provided back to back to each other.The plan-view shape of the high acoustic velocity support substrate 21(the outer peripheral shape of the high acoustic velocity supportsubstrate 21 when viewed in the thickness direction) is a square orsubstantially square shape, for example. However, the shape is notlimited to a square or substantially square shape and may be, forexample, a rectangular or substantially rectangular shape. The thicknessof the high acoustic velocity support substrate 21 is preferably, forexample, about 120 μm. The material of the high acoustic velocitysupport substrate 21 is preferably, for example, silicon. The highacoustic velocity support substrate 21 is not limited to silicon and mayinclude any one of piezoelectric bodies, for example, aluminum nitride,aluminum oxide, silicon carbide, silicon nitride, sapphire, lithiumtantalate, lithium niobate, and quartz crystal, various ceramics, forexample, alumina, zirconia, cordierite, mullite, steatite, andforsterite, magnesia diamond, a material including any one of the abovematerials as a main ingredient, and a material including a mixture ofsome of the above materials as a main ingredient.

The low acoustic velocity film 23 is preferably made of, for example,any one of silicon oxide, glass, silicon oxynitride, tantalum oxide, achemical compound provided by adding fluorine, carbon, or boron tosilicon oxide, and a material including any one of the above materialsas a main ingredient.

When the low acoustic velocity film 23 is silicon oxide, temperaturecharacteristics are significantly improved. The elastic constant oflithium tantalate has negative temperature characteristics, and theelastic constant of silicon oxide has positive temperaturecharacteristics. Therefore, with the acoustic wave device 1, theabsolute value of temperature coefficient of frequency (TCF) is reduced.In addition, the specific acoustic impedance of silicon oxide is lessthan the specific acoustic impedance of lithium tantalate. Therefore,with the acoustic wave device 1, both an increase in electromechanicalcoupling coefficient, that is, an expansion of fractional band width anda significant improvement in temperature coefficient of frequency areprovided.

The thickness of the piezoelectric body portion 24 is preferably lessthan or equal to about 3.5λ, for example, when the wave length ofacoustic waves, which is determined by the electrode finger pitch of theinterdigital transducer electrode 3, is λ. This is because the qualityfactor increases. In the acoustic wave device 1, when the thickness ofthe piezoelectric body portion 24 is less than or equal to about 2.5λ,for example, the temperature coefficient of frequency significantlyimproves. In addition, in the acoustic wave device 1, when the thicknessof the piezoelectric body portion 24 is less than or equal to about 1.5λsubstantially, adjustment of acoustic velocity becomes easy. Thethickness of the piezoelectric body portion 24 is preferably, forexample, about 600 nm.

The thickness of the low acoustic velocity film 23 is preferably lessthan or equal to about 2.0λ, for example, when the wave length ofacoustic waves, which is determined by the electrode finger pitch of theinterdigital transducer electrode 3, is λ. In the acoustic wave device1, when the thickness of the low acoustic velocity film 23 is less thanor equal to about 2.0λ, for example, membrane stress is reduced. As aresult, warpage of wafer that is the source of the high acousticvelocity support substrate 21 during manufacturing is reduced, and anefficacy percentage is able to be significantly increased andcharacteristics are able to be stabilized. The thickness of the lowacoustic velocity film 23 is, for example, about 600 nm.

(1.2.2) Reflector

The two reflectors 8 are provided on or above one main surface 241 ofthe piezoelectric body portion 24. Here, the two reflectors 8 areprovided one by one on both sides of the interdigital transducerelectrode 3 in the second direction D2.

Each of the two reflectors 8 reflects acoustic waves. Each of the tworeflectors 8 is a grating-type reflector. Each of the two reflectors 8include a plurality of electrode fingers 9. One ends of the plurality ofelectrode fingers 9 in the first direction D1 are short-circuited, andthe other ends are also short-circuited. In FIG. 1, FIG. 2A, FIG. 2B,and the like, each of the two reflectors 8 is drawn with the number ofthe electrode fingers 9 reduced to facilitate visualization. Thereflectors 8 each may be made of an appropriate metal material, forexample, aluminum (Al), copper (Cu), platinum (Pt), gold (Au), silver(Ag), titanium (Ti), nickel (Ni), chromium (Cr), molybdenum (Mo),tungsten (W), and an alloy including any one of these metals as a mainingredient. Alternatively, the reflectors 8 each may include a structurein which a plurality of metal films including any one of these metals oralloys is laminated. The thickness of each reflector 8 is preferably,for example, about 150 nm.

(1.2.3) Interdigital Transducer Electrode

The interdigital transducer electrode 3 may include an appropriate metalmaterial, for example, aluminum, copper, platinum, gold, silver,titanium, nickel, chromium, molybdenum, tungsten, and an alloy includingany one of these metals as a main ingredient. Alternatively, theinterdigital transducer electrode 3 may include a structure in which aplurality of metal films including any one of these metals or alloys islaminated. The thickness of the interdigital transducer electrode 3 ispreferably, for example, about 150 nm.

As shown in FIG. 1 and FIG. 2A, the interdigital transducer electrode 3includes a first busbar 4, a second busbar 5, a plurality of firstelectrode fingers 6, and a plurality of second electrode fingers 7.

In the interdigital transducer electrode 3, the first busbar 4 and thesecond busbar 5 are opposed to each other in a first direction D1perpendicular or substantially perpendicular to the thickness direction(up-down direction in FIG. 2B) of the piezoelectric body portion 24. Inother words, the second busbar 5 is opposed to the first busbar 4 in thefirst direction D1.

The first busbar 4 and the second busbar 5 each have a long shape havinga second direction D2 perpendicular or substantially perpendicular tothe first direction D1 as a longitudinal direction. In FIG. 1, FIG. 2A,FIG. 4, and the like, the first busbar 4 and the second busbar 5 do notlook like a long shape. This is because each of the number of the firstelectrode fingers 6 and the number of the second electrode fingers 7 isreduced to facilitate visualization. The second direction D2 is adirection along a propagation direction of acoustic waves. The seconddirection D2 is also perpendicular or substantially perpendicular to thethickness direction of the piezoelectric body portion 24.

The plurality of first electrode fingers 6 are connected to the firstbusbar 4 and have a greater width from the first busbar 4 toward thesecond busbar 5 in the first direction D1. Here, the plurality of firstelectrode fingers 6 have greater widths from the first busbar 4 along adirection perpendicular or substantially perpendicular to thelongitudinal direction of the first busbar 4. In other words, theplurality of first electrode fingers 6 have greater widths along adirection perpendicular or substantially perpendicular to thepropagation direction of acoustic waves. In the interdigital transducerelectrode 3, the plurality of first electrode fingers 6 is spaced apartfrom the second busbar 5, and a gap 31 is provided between the firstelectrode fingers 6 and the second busbar 5 that are opposed to eachother in the first direction D1. When the wave length of theabove-described acoustic waves is λ, the length of the gap 31 in thefirst direction D1 is preferably, for example, less than or equal toabout 0.5λ.

In the example of FIG. 1 and FIG. 2A, the plurality of first electrodefingers 6 each have the same or substantially the same length. A distalend portion 61 of each of the plurality of first electrode fingers 6includes a wide portion 62 having a greater width in the seconddirection D2 than a center portion 60, in the first direction D1, of thefirst electrode finger 6. Each of the plurality of first electrodefingers 6 includes a wide portion 64 (see FIG. 2A) in addition to thewide portion 62. The wide portion 64 is located between the centerportion 60 and a proximal end portion 63 (see FIG. 2A), opposite fromthe distal end portion 61, of the first electrode finger 6. The wideportion 64 has a greater width in the second direction D2 than thecenter portion 60, in the first direction D1, of the first electrodefinger 6. The wide portion 64 is located away from the first busbar 4 inthe first direction D1. In each of the plurality of first electrodefingers 6, a portion between the wide portion 62 and the wide portion 64in the first direction D1 is the center portion 60. In each of theplurality of first electrode fingers 6, the center portion 60 is longerin the first direction D1 than each of the wide portions 62, 64.

In the example of FIG. 1 and FIG. 2A, the center portion 60 of each ofthe plurality of first electrode fingers 6 has the same or substantiallythe same width. The wide portion 62 at the distal end portion 61 of eachof the plurality of first electrode fingers 6 has the same orsubstantially the same width. The wide portion 64, closer to theproximal end portion 63, of each of the plurality of first electrodefingers 6 has the same or substantially the same width. The width of thewide portion 62 at the distal end portion 61 and the width of the wideportion 64 closer to the proximal end portion 63 are the same orsubstantially the same in each of the plurality of first electrodefingers 6. Each of the plurality of first electrode fingers 6 has aline-symmetric shape with respect to a center line 6X (see FIG. 3) alongthe first direction D1. The shape of each of the wide portions 62, 64 isa rectangular or substantially rectangular shape, for example. However,the shape is not limited thereto and may be, for example, a hexagonal orsubstantially hexagonal shape, a circular or substantially circularshape, or the like.

The plurality of second electrode fingers 7 are connected to the secondbusbar 5 and have a greater width from the second busbar 5 toward thefirst busbar 4 in the first direction D1. Here, the plurality of secondelectrode fingers 7 have greater widths from the second busbar 5 along adirection perpendicular or substantially perpendicular to thelongitudinal direction of the second busbar 5. In other words, theplurality of second electrode fingers 7 have greater widths along adirection perpendicular or substantially perpendicular to thepropagation direction of acoustic waves. In the interdigital transducerelectrode 3, the plurality of second electrode fingers 7 are spacedapart from the first busbar 4, and a gap 32 is provided between thesecond electrode fingers 7 and the first busbar 4 that are opposed toeach other in the first direction D1. When the wave length of theabove-described acoustic waves is λ, the length of the gap 32 in thefirst direction D1 is preferably, for example, less than orsubstantially equal to about 0.5λ.

In the example of FIG. 1 and FIG. 2A, the plurality of second electrodefingers 7 each have the same or substantially the same length. A distalend portion 71 of each of the plurality of second electrode fingers 7includes a wide portion 72 having a greater width in the seconddirection D2 than a center portion 70, in the first direction D1, of thesecond electrode finger 7. Each of the plurality of second electrodefingers 7 includes a wide portion 74 (see FIG. 2A) in addition to thewide portion 72. The wide portion 74 is located between the centerportion 70 and a proximal end portion 73 (see FIG. 2A), opposite fromthe distal end portion 71, of the second electrode finger 7. The wideportion 74 has a greater width in the second direction D2 than thecenter portion 70, in the first direction D1, of the second electrodefinger 7. The wide portion 74 is located away from the second busbar 5in the first direction D1. In each of the plurality of second electrodefingers 7, a portion between the wide portion 72 and the wide portion 74in the first direction D1 is the center portion 70. In each of theplurality of second electrode fingers 7, the center portion 70 is longerthan each of the wide portions 72, 74 in the first direction D1.

In the example of FIG. 1 and FIG. 2A, the center portion 70 of each ofthe plurality of second electrode fingers 7 has the same orsubstantially the same width. The wide portion 72 at the distal endportion 71 of each of the plurality of second electrode fingers 7 hasthe same or substantially the same width. The wide portion 74, closer tothe proximal end portion 73, of each of the plurality of secondelectrode fingers 7 has the same or substantially the same width. Thewidth of the wide portion 72 at the distal end portion 71 and the widthof the wide portion 74 closer to the proximal end portion 73 are thesame or substantially the same in each of the plurality of secondelectrode fingers 7. Each of the plurality of second electrode fingers 7has a line-symmetric shape with respect to a center line 7X (see FIG. 3)along the first direction D1. The shape of each of the wide portions 72,74 is a rectangular or substantially rectangular shape; however, theshape is not limited thereto and may be, for example, a hexagonal orsubstantially hexagonal shape, a circular or substantially circularshape, or the like.

In the interdigital transducer electrode 3, the plurality of firstelectrode fingers 6 and the plurality of second electrode fingers 7 areprovided alternately one by one and spaced apart from each other in thesecond direction D2 perpendicular or substantially perpendicular to thefirst direction D1. Therefore, the first electrode finger 6 and thesecond electrode finger 7 adjacent to each other in the second directionD2 are spaced apart from each other.

In the interdigital transducer electrode 3, the wide portions 62 of thedistal end portions 61 of the plurality of first electrode fingers 6 andthe wide portions 74, closer to the proximal end portions 73, of thesecond electrode fingers 7 are provided alternately one by one andspaced apart from each other in the second direction D2. In addition, inthe interdigital transducer electrode 3, the wide portions 64, closer tothe proximal end portions 63, of the plurality of first electrodefingers 6 and the wide portions 72 of the distal end portions 71 of thesecond electrode fingers 7 are provided alternately one by one andspaced apart from each other in the second direction D2. The electrodefinger pitch of the interdigital transducer electrode 3 is about twicethe distance between sides respectively corresponding to the centerportion 60 of the first electrode finger 6 and the center portion 70 ofthe second electrode finger 7, adjacent to each other. The electrodefinger pitch of the interdigital transducer electrode 3 is the same orsubstantially the same value when defined by the distance between thecenter lines 6X (see FIG. 3) of the adjacent two first electrode fingers6 in the second direction D2 of the plurality of first electrode fingers6. In addition, the electrode finger pitch of the interdigitaltransducer electrode 3 is the same or substantially the same value whendefined by the distance between the center lines 7X (see FIG. 3) of theadjacent two second electrode fingers 7 in the second direction D2 ofthe plurality of second electrode fingers 7. A group of electrodefingers includes the plurality of first electrode fingers 6 and theplurality of second electrode fingers 7 spaced apart from each other inthe second direction D2 perpendicular or substantially perpendicular tothe first direction D1 and may also include the plurality of firstelectrode fingers 6 and the plurality of second electrode fingers 7 notprovided alternately and spaced apart from each other. For example, aregion in which the first electrode finger 6 and the second electrodefinger 7 are provided one by one and spaced apart from each other and aregion in which the two first electrode fingers 6 or the two secondelectrode fingers 7 are provided in the second direction D2 may bemixed.

The first busbar 4 includes opening portions 40, an inner busbar portion42, an outer busbar portion 41, and coupling portions 43. The innerbusbar portion 42 is located closer to the plurality of first electrodefingers 6 and the plurality of second electrode fingers 7 than theopening portions 40 in the first direction D1. The outer busbar portion41 is located across the opening portions 40 from the inner busbarportion 42 in the first direction D1. In other words, the outer busbarportion 41 is located away in the first direction D1 from a side wherethe plurality of first electrode fingers 6 is present. The couplingportions 43 couple the inner busbar portion 42 and the outer busbarportion 41 in the first direction D1. The coupling portions 43 arelocated on both sides of each opening portion 40 in the second directionD2. In the example of FIG. 1, each coupling portion 43 has the same orsubstantially the same width as the center portion of the firstelectrode finger 6 and is located along an extension from the firstelectrode finger 6. However, the dimensions of each coupling portion 43and the locations of the coupling portions 43 are not limited thereto.

The opening shape of each opening portion 40 is rectangular orsubstantially rectangular, for example. However, the opening shape isnot limited thereto. When the wave length of the above-describedacoustic waves is λ, the width of the inner busbar portion 42 in thefirst direction D1 is preferably, for example, less than orsubstantially equal to about 0.5λ. The length of each coupling portion43 in the first direction D1 is preferably, for example, about 2.0λ.

The first busbar 4 includes the plurality of opening portions 40.However, to facilitate visualization, the number of the first electrodefingers 6 is reduced in FIG. 1 and FIG. 2A, such that only one openingportion 40 is shown in FIG. 1 and FIG. 2A. The plurality of openingportions 40 are, for example, located at equal or substantially equalintervals in the second direction D2. In the example of FIG. 1 and FIG.2A, the opening width of each opening portion 40 in the second directionD2 is, for example, the same or substantially the same as the distancebetween the center portions 60 of the adjacent two first electrodefingers 6 in the second direction D2. Although only one opening portion40 is shown in FIG. 1 and FIG. 2A as described above, the distancebetween the two adjacent opening portions 40 in the second direction D2is, for example, the same or substantially the same as the width of thecenter portion 60 of the first electrode finger 6 in the seconddirection D2.

The second busbar 5 includes opening portions 50, an inner busbarportion 52, an outer busbar portion 51, and coupling portions 53. Theinner busbar portion 52 is located closer to the plurality of firstelectrode fingers 6 and the plurality of second electrode fingers 7 thanthe opening portions 50 in the first direction D1. The outer busbarportion 51 is located across the opening portions 50 from the innerbusbar portion 52 in the first direction D1. In other words, the outerbusbar portion 51 is located away in the first direction D1 from a sidewhere the plurality of second electrode fingers 7 is present. Thecoupling portions 53 couple the inner busbar portion 52 and the outerbusbar portion 51 in the first direction D1. The coupling portions 53are located on both sides of each opening portion 50 in the seconddirection D2. In the example of FIG. 1 and FIG. 2A, each couplingportion 53 has the same or substantially the same width as the centerportion 70 of the second electrode finger 7 and is located along anextension from the second electrode finger 7. However, the dimensions ofeach coupling portion 53 and the locations of the coupling portions 53are not limited thereto.

The opening shape of each opening portion 50 is rectangular orsubstantially rectangular, for example. However, the opening shape isnot limited thereto. When the wave length of the above-describedacoustic waves is λ, the width of the inner busbar portion 52 in thefirst direction D1 is preferably, for example, less than or equal toabout 0.5λ. The length of each coupling portion 53 in the firstdirection D1 is preferably, for example, about 2.0λ.

The acoustic wave device 1 according to the first preferred embodimentincludes a structure that significantly reduces or prevents atransverse-mode ripple by providing a piston mode in the interdigitaltransducer electrode 3. This point will be described with reference toFIG. 4.

As shown at the left side of FIG. 4, the acoustic wave device 1 includes11 regions A1 to A11 in the first direction D1 in plan view taken in thethickness direction of the acoustic wave device 1. The 11 regions A1 toA11 respectively include different portions in each of the piezoelectricbody portion 24 and the interdigital transducer electrode 3. FIG. 4shows the velocity (acoustic velocity) of acoustic waves that propagatethrough the 11 regions A1 to A11 at the right side.

In the acoustic wave device 1, of the above-described 11 regions A1 toA11, the region A6 located in the center in the first direction D1 is acenter region. The center region includes the center portions 60 of theplurality of first electrode fingers 6 and the center portions 70 of theplurality of second electrode fingers 7. In short, the center region isa region in which the center portions 60 of the plurality of firstelectrode fingers 6 and the center portions 70 of the plurality ofsecond electrode fingers 7 overlap in the second direction D2. In thecenter region, a value (duty ratio) determined by dividing the electrodefinger width (the width of each of the center portion 60 of the firstelectrode finger 6 and the center portion 70 of the second electrodefinger) by a value half the above-described electrode finger pitch ispreferably, for example, about 0.5.

In the acoustic wave device 1, of the above-described 11 regions A1 toA11, the regions A1, A11 respectively located at both ends in the firstdirection D1 are outer busbar regions. The region A1 includes the outerbusbar portion 41 of the first busbar 4. The region A11 includes theouter busbar portion 51 of the second busbar 5. The acoustic velocity ofacoustic waves in the outer busbar regions is lower than the acousticvelocity in the center region.

In the acoustic wave device 1, of the above-described 11 regions A1 toA11, the regions A2, A10 respectively located at the second from bothends in the first direction D1 are coupling regions. The region A2includes the plurality of coupling portions 43 and plurality of openingportions 40 of the first busbar 4. The region A10 includes the pluralityof coupling portions 53 and plurality of opening portions 50 of thesecond busbar 5. The acoustic velocity of acoustic waves in the couplingregions is higher than the acoustic velocity in the outer busbar regionsor the acoustic velocity in the center region.

In the acoustic wave device 1, of the above-described 11 regions A1 toA11, the regions A3, A9 respectively located at the third from both endsin the first direction D1 are inner busbar regions. The region A3includes the inner busbar portion 42 of the first busbar 4. The regionA9 includes the inner busbar portion 52 of the second busbar 5. Theacoustic velocity of acoustic waves in the inner busbar regions is lowerthan the acoustic velocity in the center region.

In the acoustic wave device 1, of the above-described 11 regions A1 toA11, the regions A4, A8 respectively located at the fourth from bothends in the first direction D1 are gap regions. The region A4 includesthe proximal end portions 63 of the plurality of first electrode fingers6 and the plurality of gaps 32. The region A8 includes the proximal endportions 73 of the plurality of second electrode fingers 7 and theplurality of gaps 31. The acoustic velocity of acoustic waves in the gapregions is higher than the acoustic velocity in the inner busbar regionsor the acoustic velocity in the center region.

In the acoustic wave device 1, of the above-described 11 regions A1 toA11, the regions A5, A7 respectively located at the fifth from both endsin the first direction D1 are wide regions. The region A5 includes thewide portions 64 of the plurality of first electrode fingers 6 and thewide portions 72 of the plurality of second electrode fingers 7. Theregion A7 includes the wide portions 62 of the plurality of firstelectrode fingers 6 and the wide portions 74 of the plurality of secondelectrode fingers 7. The acoustic velocity of acoustic waves in the wideregions is lower than the acoustic velocity in the center region.

In the acoustic wave device 1, since the interdigital transducerelectrode 3 is provided as described above, the low acoustic velocityregions (the regions A5, A3 and the regions A7, A9) are present on theouter side of the center region (the region A6), and the high acousticvelocity regions A2, A10 are present on the outer side of the lowacoustic velocity regions. Therefore, the acoustic wave device 1 is ableto provide a piston mode, so a transverse-mode ripple is significantlyreduced or prevented.

(1.3) Potentials of Interdigital Transducer Electrode and Reflectors

FIG. 5 shows an electric charge distribution in the surface (includingthe surface of the interdigital transducer electrode 3 and the one mainsurface 241 of the piezoelectric body portion 24) of the acoustic wavedevice 1 according to the first preferred embodiment. A precondition forthe electric charge distribution shown in FIG. 5 includes a conditionthat an excitation phenomenon of surface acoustic waves is occurring inthe region associated with the interdigital transducer electrode 3, acondition that each reflector 8 is electrically short-circuited(short-circuited grating), and a condition that no excitation phenomenonof surface acoustic waves is occurring in the regions associated withthe reflectors 8 (since the reflectors 8 are electricallyshort-circuited, a driving voltage that causes a piezoelectric effect iszero). Here, the principle that the electric charge distribution shownin FIG. 5 occurs is as follows. An edge effect (also referred to ascut-edge effect) occurs in a boundary region between a region whereexcitation of surface acoustic waves is occurring and a region where noexcitation is occurring. Because of the edge effect, the amount ofelectric charge in a boundary region locally increases as compared tothe amount of electric charge in regions around the boundary region.Therefore, in the acoustic wave device 1, the electric chargedistribution as shown in FIG. 5 occurs.

As is apparent from FIG. 5, in the acoustic wave device 1, in the seconddirection D2 in which a group of electrode fingers including theplurality of first electrode fingers 6 and the plurality of secondelectrode fingers 7 is provided, the amount of electric charge at eachend of the interdigital transducer electrode 3 is greater than theamount of electric charge in the center of the interdigital transducerelectrode 3. In the direction along the second direction D2, the amountof electric charge at an end, closer to the interdigital transducerelectrode 3, of each reflector 8 is greater than the amount of electriccharge at an end away from the interdigital transducer electrode 3.Accordingly, in the acoustic wave device 1, for example, the density ofelectric lines of force tends to increase between the outer busbarportion 41 having a relatively higher potential between the two outerbusbar portions 41, 51 and the reflector 8 adjacent to the outer busbarportion 41.

Hereinafter, for the above-described group of electrode fingers, thesecond electrode finger 7 located at the left-side end in FIG. 1 andFIG. 2A in the second direction D2 may be referred to as secondelectrode finger 7L, and the second electrode finger located at theright-side end in FIG. 1 and FIG. 2A may be referred to as secondelectrode finger 7R.

In the interdigital transducer electrode 3, of the inner busbar portion42 of the first busbar 4 and the inner busbar portion 52 of the secondbusbar 5, the inner busbar portion 42 of the first busbar 4 is close tothe second electrode fingers 7L, 7R. The outer busbar portion 41different in potential from the second electrode fingers 7L, 7R islocated on an inner side in the second direction D2 relative to thecenter portion 70, in the first direction D1, of the second electrodefinger 7L located at one end and the center portion 70, in the firstdirection D1, of the second electrode finger 7R located at the other endof the above-described group of electrode fingers.

In FIG. 3, for the sake of convenience of description, in theinterdigital transducer electrode 3, the label “H” is assigned to theportion (high potential portion) electrically connected to the firstterminal 11, and the label “E” is assigned to the portion (low potentialportion) electrically connected to the second terminals 12. The highpotential portion is different in potential from the low potentialportion. The high potential portion is a portion higher in potentialthan the low potential portion. The labels “H”, “E” are not signs andare not actually present. FIG. 3 is an enlarged view including thesecond electrode finger 7 located at the left-side end in FIG. 1 andFIG. 2A and the inner busbar portion 42 close to this second electrodefinger 7. In FIG. 1 and FIG. 2A, the high potential portions (firstconductive portions including the first busbar 4 and the plurality offirst electrode fingers 6) to which the label “H” is assigned aredifferent in potential from low potential portions (second conductiveportions including the second busbar 5 and the plurality of secondelectrode fingers 7) to which the label “E” is assigned.

(1.4) Advantageous Effects

The acoustic wave device 1 according to the first preferred embodimentincludes the first terminal 11, the second terminals 12, thepiezoelectric body portion 24, the interdigital transducer electrode 3,and the reflectors 8. Each second terminal has a lower potential thanthe first terminal 11. The interdigital transducer electrode 3 isprovided on or above the piezoelectric body portion 24, and electricallyconnected to the first terminal 11 and the second terminals 12. Thereflectors 8 are provided on or above the piezoelectric body portion 24and electrically connected to the second terminals 12. The interdigitaltransducer electrode 3 includes the first busbar 4, the second busbar 5,the plurality of first electrode fingers 6, and the plurality of secondelectrode fingers 7. The first busbar 4 is electrically connected to thefirst terminal 11. The second busbar 5 is opposed to the first busbar 4in the first direction D1 and electrically connected to the secondterminals 12. The plurality of first electrode fingers 6 are connectedto the first busbar 4 and have a greater width from the first busbar 4toward the second busbar 5 in the first direction D1. The plurality ofsecond electrode fingers 7 are connected to the second busbar 5 and havea greater width from the second busbar 5 toward the first busbar 4 inthe first direction D1. The plurality of first electrode fingers 6 andthe plurality of second electrode fingers 7 are provided alternately oneby one and spaced apart from each other in the second direction D2perpendicular or substantially perpendicular to the first direction D1.At least one electrode finger (first electrode finger 6) of theplurality of first electrode fingers 6 includes the wide portion 62having a greater width in the second direction D2 than the centerportion 60, in the first direction D1, of the at least one electrodefinger (first electrode finger 6). At least one electrode finger (secondelectrode finger 7) of the plurality of second electrode fingers 7includes the wide portion 72 having a greater width in the seconddirection D2 than the center portion 70, in the first direction D1, ofthe at least one electrode finger (second electrode finger 7). The firstbusbar 4 includes the opening portions 40, the inner busbar portion 42,the outer busbar portion 41, and the coupling portions 43. The secondbusbar 5 includes the opening portions 50, the inner busbar portion 52,the outer busbar portion 51, and the coupling portions 53. The innerbusbar portion 42 is located closer to the plurality of first electrodefingers 6 and the plurality of second electrode fingers 7 than theopening portions in the first direction D1. The inner busbar portion 52is located closer to the plurality of first electrode fingers 6 and theplurality of second electrode fingers 7 than the opening portions 50 inthe first direction D1. The outer busbar portion 41 is located acrossthe opening portions 40 from the inner busbar portion 42 in the firstdirection D1. The outer busbar portion 51 is located across the openingportions 50 from the inner busbar portion 52 in the first direction D1.The coupling portions 43 couple the inner busbar portion 42 and theouter busbar portion 41 in the first direction D1. The coupling portions53 couple the inner busbar portion 52 and the outer busbar portion 51 inthe first direction D1. In the interdigital transducer electrode 3,where, of the group of electrode fingers including the plurality offirst electrode fingers 6 and the plurality of second electrode fingers7, the electrode finger (the second end electrode finger 7L or thesecond end electrode finger 7R) located at one end in the seconddirection D2 is a first end electrode finger and the electrode finger(the second end electrode finger 7R or the second end electrode finger7L) located at the other end is a second end electrode finger, the firstend electrode finger is located between the reflector 8 and the secondend electrode finger in the second direction D2.

The outer busbar portion (outer busbar portion 41) of one (first busbar4) of the first busbar 4 and the second busbar 5, not connected to thefirst end electrode finger, is located on an inner side in the seconddirection D2 relative to the center portion (center portion 70), in thefirst direction D1, of the first end electrode finger.

Thus, with the acoustic wave device 1 according to the first preferredembodiment, the interdigital transducer electrode 3 includes theabove-described features, such that interference with a piston mode issignificantly reduced or prevented. In addition, with the acoustic wavedevice 1 according to the first preferred embodiment, for the outerbusbar portion 41 not connected to the second electrode fingers 7L, 7R,surge breakdown due to ESD between the outer busbar portion 41 and thereflectors 8 is less likely to occur, so significant improvement in ESDtolerance is provided. Thus, with the acoustic wave device 1 accordingto the first preferred embodiment, ESD tolerance is significantlyimproved while interference with a piston mode is significantly reducedor prevented.

The acoustic wave device 1 according to the first preferred embodimentincludes the two reflectors 8. The reflectors are provided one by one onboth sides of the interdigital transducer electrode 3 in the seconddirection D2. In the acoustic wave device 1 according to the firstpreferred embodiment, the outer busbar portion 41 of the first busbar 4not connected to the second electrode fingers 7L, 7R is located on aninner side in the second direction D2 relative to the wide portions 72of the second electrode finger 7L and the wide portion 72 of the secondelectrode finger 7R. Thus, with the acoustic wave device 1, surgebreakdown is less likely to occur and ESD tolerance significantlyimproves as compared to when the wide portion 72 of the second electrodefinger 7L and the outer busbar portion 41 overlap in the first directionD1.

In the acoustic wave device 1, the outer busbar portion 41 is located onan inner side in the second direction D2 relative to the secondelectrode finger 7L and the second electrode finger 7R and does notoverlap the second electrode finger 7L or the second electrode finger 7Rin the first direction D1. Thus, with the acoustic wave device 1, theshortest distance between the outer busbar portion 41 and each reflector8 is have a greater width, so ESD tolerance is further improved.

In the acoustic wave device 1, one (left in the second direction D2)side 42L, along the first direction D1, of the inner busbar portion 42of the first busbar 4 not connected to the second electrode fingers 7L,7R and a (left) side 72LL, away from the second electrode finger 7R, ofthe wide portion 72 of the second electrode finger 7L are aligned in astraight line or substantially in a straight line, and the other (rightin the second direction D2) side 42R, along the first direction D1, ofthe inner busbar portion 42 and a (right) side 72RR, away from thesecond electrode finger 7L, of the wide portion 72 of the secondelectrode finger 7R are aligned in a straight line or substantially in astraight line. Thus, with the acoustic wave device 1, ESD tolerance issignificantly improved by changing only the shape of the outer busbarportion 41 without changing the shape of the inner busbar portion 42, soESD tolerance is further improved while interference with a piston modeis significantly reduced or prevented.

In the interdigital transducer electrode 3, of the group of electrodefingers including the plurality of first electrode fingers 6 and theplurality of second electrode fingers 7, the outer busbar portion 41 ofthe first busbar 4 not connected to the second electrode finger 7Llocated at one end in the second direction D2 or the second electrodefinger 7R located at the other end is located on an inner side in thesecond direction D2 relative to the inner busbar portion 42 close to thesecond electrode fingers 7L, 7R respectively located at both ends in thesecond direction D2.

Thus, with the acoustic wave device 1 according to the first preferredembodiment, the outer busbar portion 41 of the first busbar 4 notconnected to the second electrode finger 7L or the second electrodefinger 7R is able to significantly reduce or prevent surge breakdown dueto ESD. Thus, with the acoustic wave device 1 according to the firstpreferred embodiment, ESD tolerance is significantly improved.

(1.5) First Modification of First Embodiment

In an acoustic wave device 1 a according to a first modification of thefirst preferred embodiment shown in FIG. 5, the left side of the outerbusbar portion 41 and the right side of the wide portion 72 of thesecond electrode finger 7L are aligned in a straight line orsubstantially in a straight line. In addition, the right side of theouter busbar portion 41 and the left side of the wide portion 72 of thesecond electrode finger 7R (see FIG. 2A) are aligned in a straight lineor substantially in a straight line. Other features of the acoustic wavedevice 1 a according to the first modification are the same as orsimilar to those of the acoustic wave device 1 according to the firstpreferred embodiment, so the drawings and description thereof areomitted.

With the acoustic wave device 1 a according to the first modification,the length of the outer busbar portion 41 in the second direction D2 isincreased as compared to the acoustic wave device 1 according to thefirst preferred embodiment, such that interference with a piston mode isfurther reduced or prevented.

(1.6) Other Modifications of First Embodiment

The number of the plurality of first electrode fingers 6 and the numberof the plurality of second electrode fingers 7 in the interdigitaltransducer electrode 3 are not limited. Here, in the interdigitaltransducer electrode 3, the electrode fingers respectively located atboth ends in the second direction D2 of the group of electrode fingersare not limited to the second electrode fingers 7. For example, of thegroup of electrode fingers, the electrode finger located at one end inthe second direction D2 may be the second electrode finger 7, and theelectrode finger located at the other end may be the first electrodefinger 6. Accordingly, the inner busbar portion 42 of the first busbar 4is close to the second electrode finger 7 located at one end, and theinner busbar portion 52 of the second busbar 5 is close to the firstelectrode finger 6 located at the other end. Of the group of electrodefingers, the electrode fingers respectively located at one end and theother end in the second direction D2 may be the first electrode fingers6. Accordingly, the inner busbar portion 52 of the second busbar 5 isclose to the first electrode fingers 6 respectively located at one endand the other end. The group of electrode fingers only needs to includethe plurality of first electrode fingers 6 and the plurality of secondelectrode fingers 7 spaced apart from each other in the second directionD2 perpendicular or substantially perpendicular to the first directionD1. For example, in an acoustic wave device of one modification, aregion in which the first electrode finger 6 and the second electrodefinger 7 are provided one by one and spaced apart from each other and aregion in which the two first electrode fingers 6 or the two secondelectrode fingers 7 are provided in the second direction D2 may bemixed. With the acoustic wave device of any one of these modificationsas well, the outer busbar portion not connected to at least oneelectrode finger of the two electrode fingers respectively located oneby one at one end and the other end in the second direction D2 of thegroup of electrode fingers is located on an inner side in the seconddirection D2 relative to the center portion, in the first direction D1,of the at least one electrode finger, ESD tolerance is significantlyimproved. At least one first electrode finger 6 of the plurality offirst electrode fingers 6 in the interdigital transducer electrode 3only needs to include the wide portion 62, and at least one secondelectrode finger 7 of the plurality of second electrode fingers 7 in theinterdigital transducer electrode 3 only needs to include the wideportion 72.

In the interdigital transducer electrode 3, of the group of electrodefingers, at least one electrode finger may have three or more wideportions.

The acoustic wave device 1 may further include an electricallyconductive first bump provided on or above the first terminal 11 and anelectrically conductive second bump provided on or above each of thesecond terminals 12. The number of the second terminals 12 is notlimited to a multiple number and may be, for example, one.

Second Preferred Embodiment (2.1) Overall Configuration of Acoustic WaveDevice

Hereinafter, an acoustic wave device 1 b according to a second preferredembodiment of the present invention will be described with reference tothe drawings.

The acoustic wave device 1 b according to the second preferredembodiment is a longitudinally coupled resonator filter, and, as shownin FIG. 7 to FIG. 10, includes the first terminals (for example, signalterminals) 11, the second terminals (for example, ground terminals) 12,the piezoelectric body portion 24, and a plurality of the interdigitaltransducer electrodes 3. The piezoelectric body portion 24 is made of apiezoelectric material. The plurality of interdigital transducerelectrodes 3 is provided on or above the piezoelectric body portion 24.The acoustic wave device 1 b according to the second preferredembodiment further includes the two reflectors 8. In FIG. 7 and FIG. 8,dot hatching is applied to the plurality of interdigital transducerelectrodes 3 and the reflectors 8. These hatchings do not representcross sections and are provided to clearly show the relationship amongthe plurality of interdigital transducer electrodes 3, the reflectors 8,and the piezoelectric body portion 24. As for the acoustic wave device 1b according to the second preferred embodiment, like reference numeralsdenote similar components to those of the acoustic wave device 1 (seeFIG. 1 to FIG. 4) according to the first preferred embodiment, and thedescription thereof may be omitted.

(2.2) Components of Acoustic Wave Device

Next, the components of the acoustic wave device 1 b will be describedwith reference to the drawings.

(2.2.1) Multilayer Board

In the acoustic wave device 1 b according to the second preferredembodiment, the piezoelectric body portion 24 is a piezoelectric film,and the plurality of interdigital transducer electrodes 3 is provided onor above a multilayer board 2 b including the piezoelectric body portion24. The plan-view shape (the outer peripheral shape of the high acousticvelocity support substrate 21 when viewed in the thickness direction) ofthe high acoustic velocity support substrate 21 (see FIG. 9) in themultilayer board 2 b is a rectangular or substantially rectangularshape, for example. However, the shape is not limited to a rectangularor substantially rectangular shape and may be, for example, a square orsubstantially square shape.

(2.2.2) Reflector

The two reflectors 8 are provided on or above the piezoelectric bodyportion 24. Here, the two reflectors 8 each are provided one by oneacross the interdigital transducer electrode 3 at any one of both sidesof the three interdigital transducer electrodes 3 in the seconddirection D2 from the center interdigital transducer electrode 3.Hereinafter, for the sake of convenience of description, when the threeinterdigital transducer electrodes 3 are distinguished from one another,of the plurality of interdigital transducer electrodes 3, one of theadjacent two interdigital transducer electrodes 3 in the seconddirection D2 may be referred to as first interdigital transducerelectrode 3A and the other may be referred to as second interdigitaltransducer electrode 3B. In the example of FIG. 7 and FIG. 8, of thethree interdigital transducer electrodes 3, the center interdigitaltransducer electrode 3 is referred to as first interdigital transducerelectrode 3A, and the interdigital transducer electrodes 3 at both endsare referred to as second interdigital transducer electrodes 3B.

(2.2.3) Interdigital Transducer Electrode

In the acoustic wave device 1 b according to the second preferredembodiment, the three interdigital transducer electrodes 3 are providedin the second direction D2. Each of the three interdigital transducerelectrodes 3 includes the first busbar 4, the second busbar 5, theplurality of first electrode fingers 6, and the plurality of secondelectrode fingers 7.

The first busbar 4 includes the opening portions 40, the inner busbarportion 42, the outer busbar portion 41, and the coupling portions 43.The second busbar 5 includes the opening portions 50, the inner busbarportion 52, the outer busbar portion 51, and the coupling portions 53.In the interdigital transducer electrode 3, the wide portions 62 of thedistal end portions 61 of the plurality of first electrode fingers 6 andthe wide portions 74, closer to the proximal end portions 73, of thesecond electrode fingers 7 are provided alternately one by one andspaced apart from each other in the second direction D2. In addition, inthe interdigital transducer electrode 3, the wide portions 64, closer tothe proximal end portions 63, of the plurality of first electrodefingers 6 and the wide portions 72 of the distal end portions 71 of thesecond electrode fingers 7 are provided alternately one by one andspaced apart from each other in the second direction D2.

(2.3) Potential of Interdigital Transducer Electrode

In FIG. 7 and FIG. 8, for the sake of convenience of description, thelabel “H” is assigned to portions (high potential portions) electricallyconnected to the first terminals (signal terminals) 11 in theinterdigital transducer electrodes 3, and the label “E” is assigned toportions (low potential portions) electrically connected to the secondterminals (ground terminals) 12 in the interdigital transducerelectrodes 3 and the reflectors 8. The high potential portions aredifferent in potential from the low potential portions. The highpotential portions are portions higher in potential than the lowpotential portions. The labels “H”, “E” are not signs and are notactually present.

The acoustic wave device 1 b includes the two first terminals 11 and thetwo second terminals 12. When the two first terminals 11 aredistinguished from each other, one is referred to as first terminal 11A,and the other is referred to as first terminal 11B. When the two secondterminals 12 are distinguished from each other, one is referred to assecond terminal 12A, and the other is referred to as second terminal12B.

The first busbar 4 of the first interdigital transducer electrode 3A iselectrically connected to the first terminal 11A. The acoustic wavedevice 1 b includes the first wiring layer 13 (13A) that electricallyconnects the first terminal 11A and the first busbar 4 of the firstinterdigital transducer electrode 3A. The second busbar 5 of the firstinterdigital transducer electrode 3A is electrically connected to thesecond terminal 12A and the second terminal 12B. The acoustic wavedevice 1 b includes the second wiring layer 14 (14A) that electricallyconnects the second terminal 12A, the second terminal 12B, and thesecond busbar 5 of the first interdigital transducer electrode 3A. Inthe first interdigital transducer electrode 3A, the second busbar 5 hasa lower potential than the first busbar 4.

The first busbar 4 of each second interdigital transducer electrode 3Bis electrically connected to the second terminal 12B. The acoustic wavedevice 1 b includes the second wiring layer 14 (14B) that electricallyconnects the second terminal 12B and the first busbar 4 of each secondinterdigital transducer electrode 3B. The second busbar 5 of each secondinterdigital transducer electrode 3B is electrically connected to thefirst terminal 11B. The acoustic wave device 1 b includes the firstwiring layer 13 (13B) that electrically connects the first terminal 11Band the second busbar 5 of each second interdigital transducer electrode3B. In each second interdigital transducer electrode 3B, the firstbusbar 4 has a lower potential than the second busbar 5.

Each reflector 8 is electrically connected to the second terminal 12Aand the second terminal 12B. Each reflector 8 has a lower potential thanthe second busbar 5 of each second interdigital transducer electrode 3B.

The acoustic wave device 1 b includes an electrically insulating layer15 that electrically insulates the first wiring layer 13 (13A) and thesecond wiring layer 14 (14B) from each other. The electricallyinsulating layer 15 is provided on or above the piezoelectric bodyportion 24 and partially interposed between the first wiring layer 13(13A) and the second wiring layer (14B). The acoustic wave device 1 bincludes an electrically insulating layer 16 that electrically insulatesthe first wiring layer 13 (13B) and the second wiring layer 14 (14A)from each other. The electrically insulating layer 16 is provided on orabove the piezoelectric body portion 24 and partially interposed betweenthe first wiring layer 13 (13B) and the second wiring layer (14A).

The acoustic wave device 1 b may further include an electricallyconductive first bump provided on or above each of the first terminals11 and an electrically conductive second bump provided on or above eachof the second terminals 12. The number of the first terminals 11 and thenumber of the second terminals each are not limited to a multiple numberand may be, for example, one.

FIG. 10 is an enlarged view including the first electrode finger 6located at the left-side end of the center first interdigital transducerelectrode 3A in FIG. 7 and FIG. 8 and the first electrode finger 6located at the right-side end of the left-side second interdigitaltransducer electrode 3B in FIG. 7 and FIG. 8. In FIG. 7, FIG. 8, andFIG. 10, the high potential portions to which the label “H” is assignedare different in potential from the low potential portions to which thelabel “E” is assigned. For example, in FIG. 10, the first electrodefinger 6 located at the left-side end of the first interdigitaltransducer electrode 3A and the first electrode finger 6 located at theright-side end of the second interdigital transducer electrode 3B aredifferent in potential. In FIG. 10, the first electrode finger 6 locatedat the left-side end of the first interdigital transducer electrode 3Aand the second busbar 5 of the first interdigital transducer electrode3A, close to this first electrode finger 6, are different in potential.In FIG. 10, the first electrode finger 6 located at the right-side endof the second interdigital transducer electrode 3B and the second busbar5 of the second interdigital transducer electrode 3B, close to thisfirst electrode finger 6, are different in potential. The second busbar5 of the first interdigital transducer electrode 3A and the secondbusbar 5 of the second interdigital transducer electrode 3B aredifferent in potential.

FIG. 11 shows an electric charge distribution in the surface (includingthe surfaces of the three interdigital transducer electrodes 3 and theone main surface 241 of the piezoelectric body portion 24) of theacoustic wave device 1 b according to the second preferred embodiment. Aprecondition for the electric charge distribution shown in FIG. 11includes a condition that an excitation phenomenon of surface acousticwaves is occurring in the region associated with the first interdigitaltransducer electrode 3A and each region associated with the secondinterdigital transducer electrode 3B, a condition that the regionassociated with the first interdigital transducer electrode 3A and eachregion associated with the second interdigital transducer electrode 3Bare respectively connected to different electrical terminals (the firstterminal 11A and the first terminal 11B), a condition that eachreflector 8 is electrically short-circuited (short-circuited grating),and a condition that no excitation phenomenon of surface acoustic wavesis occurring in the regions associated with the reflectors 8 (since thereflectors 8 are electrically short-circuited, a driving voltage thatcauses a piezoelectric effect is zero). Here, the principle that theelectric charge distribution shown in FIG. 11 occurs is as follows. Anedge effect (also referred to as cut-edge effect) occurs in a boundaryregion between a region where excitation of surface acoustic waves isoccurring and a region where no excitation is occurring. An edge effectalso occurs in a boundary region between two regions in which the statesof excitation of surface acoustic waves are different from each other.Because of the edge effect, the amount of electric charge in a boundaryregion locally increases as compared to the amount of electric charge inregions around the boundary region. An edge effect, in principle, mayoccur in applicable various boundary regions when the states ofexcitation of surface acoustic waves are different from each other.However, in the case of the acoustic wave device 1 b (longitudinallycoupled resonator-type filter) according to the second preferredembodiment, as shown in FIG. 11, the amount of electric charge mostlylocally concentrates in the boundary region between the regionassociated with the first interdigital transducer electrode 3A and eachregion associated with the second interdigital transducer electrode 3Band in the boundary region between each region associated with thesecond interdigital transducer electrode 3B and the region associatedwith the reflector 8. Therefore, in the acoustic wave device 1 baccording to the second preferred embodiment, the electric chargedistribution as shown in FIG. 11 occurs.

As is apparent from FIG. 11, in the acoustic wave device 1 b, in thesecond direction D2 in which a group of electrode fingers including theplurality of first electrode fingers 6 and the plurality of secondelectrode fingers 7 is provided, the amount of electric charge at eachend of the interdigital transducer electrode 3 is greater than theamount of electric charge in the center of the interdigital transducerelectrode 3. Accordingly, in the acoustic wave device 1 b, for example,the density of electric lines of force tends to increase between theouter busbar portions 51 of the adjacent interdigital transducerelectrodes 3. In the direction along the second direction D2, the amountof electric charge at an end, closer to the interdigital transducerelectrode 3, of each reflector 8 is greater than the amount of electriccharge at an end away from the interdigital transducer electrode 3.Accordingly, in the acoustic wave device 1 b, for example, the densityof electric lines of force tends to increase between the outer busbarportion 41 having a relatively higher potential between the two outerbusbar portions 41, 51 and the reflector 8 adjacent to the outer busbarportion 41.

(2.4) Advantageous Effects

The acoustic wave device 1 b according to the second preferredembodiment includes the first terminals 11, the second terminals 12, thepiezoelectric body portion 24, and the plurality of interdigitaltransducer electrodes 3. Each second terminal 12 has a lower potentialthan each first terminal 11. The plurality of interdigital transducerelectrodes 3 are provided on or above the piezoelectric body portion 24and electrically connected to the first terminals 11 and the secondterminals 12. Each of the plurality of interdigital transducerelectrodes 3 includes the first busbar 4, the second busbar 5, theplurality of first electrode fingers 6, and the plurality of secondelectrode fingers 7. The second busbar 5 is opposed to the first busbar4 in the first direction D1. The plurality of first electrode fingers 6are connected to the first busbar 4 and have a greater width from thefirst busbar 4 toward the second busbar 5 in the first direction D1. Theplurality of second electrode fingers 7 are connected to the secondbusbar 5 and have a greater width from the second busbar 5 toward thefirst busbar 4 in the first direction D1. The plurality of firstelectrode fingers 6 and the plurality of second electrode fingers 7 areprovided alternately one by one and spaced apart from each other in thesecond direction D2 perpendicular or substantially perpendicular to thefirst direction D1. Each of the plurality of first electrode fingers 6includes the wide portion 62 having a greater width in the seconddirection D2 than the center portion 60 in the first direction D1. Eachof the plurality of second electrode fingers 7 includes the wide portion72 having a greater width in the second direction D2 than the centerportion 70 in the first direction D1. The first busbar 4 includes theopening portions 40, the inner busbar portion 42, the outer busbarportion 41, and the coupling portions 43. The second busbar 5 includesthe opening portions 50, the inner busbar portion 52, the outer busbarportion 51, and the coupling portions 53. The inner busbar portion 42 islocated closer to the plurality of first electrode fingers 6 and theplurality of second electrode fingers 7 than the opening portions 40 inthe first direction D1. The inner busbar portion 52 is located closer tothe plurality of first electrode fingers 6 and the plurality of secondelectrode fingers 7 than the opening portions 50 in the first directionD1. The outer busbar portion 41 is located across the opening portions40 from the inner busbar portion 42 in the first direction D1. The outerbusbar portion 51 is located across the opening portions 50 from theinner busbar portion 52 in the first direction D1. The coupling portions43 couple the inner busbar portion 42 and the outer busbar portion 41 inthe first direction D1. The coupling portions 53 couple the inner busbarportion 52 and the outer busbar portion 51 in the first direction Dl.Where, of the plurality of interdigital transducer electrodes 3, one ofthe adjacent two interdigital transducer electrodes 3 in the seconddirection D2 is the first interdigital transducer electrode 3A and theother one is the second interdigital transducer electrode 3B, thedistance between the outer busbar portion 51 not connected to, of thegroup of electrode fingers including the plurality of first electrodefingers 6 and the plurality of second electrode fingers 7, the firstelectrode finger 6 closest to the second interdigital transducerelectrode 3B in the first interdigital transducer electrode 3A and theouter busbar portion 51 not connected to, of the group of electrodefingers including the plurality of first electrode fingers 6 and theplurality of second electrode fingers 7, the first electrode finger 6closest to the first interdigital transducer electrode 3A in the secondinterdigital transducer electrode 3B is greater than the distancebetween the center portion 60 of the first electrode finger 6 closest tothe second interdigital transducer electrode 3B in the firstinterdigital transducer electrode 3A and the center portion 60 of thefirst electrode finger closest to the first interdigital transducerelectrode 3A in the second interdigital transducer electrode 3B.

Thus, with the acoustic wave device 1 b according to the secondpreferred embodiment, surge breakdown due to ESD between the outerbusbar portion 51 of the first interdigital transducer electrode 3A andthe outer busbar portion 51 of the second interdigital transducerelectrode 3B is significantly reduced or prevented, such that ESDtolerance is significantly improved.

In the acoustic wave device 1 b according to the second preferredembodiment, for the first interdigital transducer electrode 3A, theouter busbar portion 51 is located on an inner side in the seconddirection D2 relative to the inner busbar portion 52. Thus, with theacoustic wave device 1 b, in comparison with the case where the outerbusbar portion 51 of the first interdigital transducer electrode 3A, aswell as the inner busbar portion 52, overlaps in the first direction D1each of the first electrode fingers 6 respectively located one by one atone end and the other end in the second direction D2 of the group ofelectrode fingers, surge breakdown is less likely to occur, such thatESD tolerance significantly improves. In the acoustic wave device 1 baccording to the second preferred embodiment, for the secondinterdigital transducer electrode 3B, the outer busbar portion 51 islocated on an inner side in the second direction D2 relative to theinner busbar portion 52. Thus, with the acoustic wave device 1 b, incomparison with the case where the outer busbar portion 51 of the secondinterdigital transducer electrode 3B, as well as the inner busbarportion 52, overlaps in the first direction D1 each of the firstelectrode fingers 6 respectively located one by one at one end and theother end in the second direction D2 of the group of electrode fingers,surge breakdown is less likely to occur, so ESD tolerance significantlyimproves.

In each of the first interdigital transducer electrode 3A and the secondinterdigital transducer electrode 3B of the acoustic wave device 1 baccording to the second preferred embodiment, the outer busbar portion51 is located on an inner side in the second direction D2 relative tothe inner busbar portion 52. In the acoustic wave device 1 b, from theviewpoint of significantly reducing or preventing a transverse-moderipple by providing a piston mode, of a state where the inner busbarportion 52 overlaps in the first direction D1 each of the firstelectrode fingers 6 located one by one at one end and the other end inthe second direction D2 of the group of electrode fingers and a statewhere the outer busbar portion 51 overlaps in the first direction D1each of the first electrode fingers 6 respectively located at both endsin the second direction D2 of the group of electrode fingers, the formerone is more important. Thus, with the acoustic wave device 1 b accordingto the second preferred embodiment, ESD tolerance is significantlyimproved while interference with a piston mode is significantly reducedor prevented. With the acoustic wave device 1 b, of the inner busbarportion 52 and the outer busbar portion 51, only the inner busbarportion 52 overlaps in the first direction D1 each of the firstelectrode fingers 6 located one by one at one end and the other end inthe second direction D2 of the group of electrode fingers, so ESDtolerance is further improved while interference with a piston mode issignificantly reduced or prevented.

(2.5) First Modification of Second Embodiment

An acoustic wave device 1 c according to a first modification of thesecond preferred embodiment shown in FIG. 12 differs from the acousticwave device 1 b according to the second preferred embodiment in that thelength of the outer busbar portion 51 in each of the plurality ofinterdigital transducer electrodes 3 is greater than that in theacoustic wave device 1 b according to the second preferred embodiment.The other features of the acoustic wave device 1 c according to thefirst modification are the same as or similar to that of the acousticwave device 1 b according to the second preferred embodiment, so thedrawings and description thereof are omitted.

In the acoustic wave device 1 c according to the first modification, thedistance between the inner busbar portions 52 of the adjacent twointerdigital transducer electrodes 3 is the same or substantially thesame as the distance between sides close to each other in the adjacentwide portions 62 in the adjacent two interdigital transducer electrodes3. In the acoustic wave device 1 c according to the first modification,the distance between the outer busbar portions 51 of the adjacent twointerdigital transducer electrodes 3 is the same or substantially thesame as the distance between sides opposite from the sides adjacent toor in a vicinity of each other in the adjacent wide portions 62 in theadjacent two interdigital transducer electrodes 3.

In the acoustic wave device 1 c, a side, closer to the secondinterdigital transducer electrode 3B, of the outer busbar portion 51 ofthe first interdigital transducer electrode 3A and a side, closer to thesecond electrode finger 7, of the wide portion 62 of the first electrodefinger 6 closest to the second interdigital transducer electrode 3B ofthe above-described group of electrode fingers of the first interdigitaltransducer electrode 3A are aligned in a straight line or substantiallyin a straight line. In the acoustic wave device 1 c, a side, closer tothe first interdigital transducer electrode 3A, of the outer busbarportion 51 of the second interdigital transducer electrode 3B and aside, closer to the second electrode finger 7, of the wide portion 62 ofthe first electrode finger 6 closest to the first interdigitaltransducer electrode 3A of the above-described group of electrodefingers of the second interdigital transducer electrode 3B are alignedin a straight line or substantially in a straight line.

With the acoustic wave device 1 c according to the first modification,the length of the outer busbar portion 51 is increased as compared tothe acoustic wave device 1 b according to the second preferredembodiment, such that interference with a piston mode is significantlyreduced or prevented.

(2.6) Second Modification of Second Embodiment

As shown in FIG. 13 and FIG. 14, an acoustic wave device 1 d accordingto a second modification of the second preferred embodiment differs fromthe acoustic wave device 1 b (see FIG. 7 to FIG. 11) according to thesecond preferred embodiment in that, in only the left-side secondinterdigital transducer electrode 3B of the three interdigitaltransducer electrodes 3, the outer busbar portion 51 of the secondbusbar 5 is located on an inner side in the second direction D2 relativeto the inner busbar portion 52 at a side closer to the firstinterdigital transducer electrode 3A. The other features of the acousticwave device 1 d according to the second modification are the same as orsimilar to that of the acoustic wave device 1 b according to the secondpreferred embodiment, so the drawings and description thereof areomitted.

In the acoustic wave device 1 d according to the second modification, ineach of the center first interdigital transducer electrode 3A and theright-side second interdigital transducer electrode 3B of the threeinterdigital transducer electrodes 3, the outer busbar portion 51 of thesecond busbar 5 overlaps the inner busbar portion 52 in the firstdirection D1 over the entire or substantially the entire length. Here,the length of the outer busbar portion 51 is the same or substantiallythe same as the length of the inner busbar portion 52. In the outerbusbar portion and the inner busbar portion 52, left sides in the seconddirection D2 are aligned in a straight line or substantially in astraight line, and right sides are aligned in a straight line orsubstantially in a straight line.

With the acoustic wave device 1 d according to the second modification,interference with a piston mode is significantly reduced or prevented ascompared to the acoustic wave device 1 b according to the secondpreferred embodiment. In the acoustic wave device 1 d according to thesecond modification, for the second interdigital transducer electrode3B, the outer busbar portion 51 of the second busbar 5 is located on aninner side in the second direction D2 relative to the inner busbarportion 52 at a side closer to the first interdigital transducerelectrode 3A. Thus, with the acoustic wave device 1 d according to thesecond modification, surge breakdown due to ESD between the outer busbarportion 51 of the second interdigital transducer electrode 3B and theouter busbar portion 51 of the first interdigital transducer electrode3A is significantly reduced or prevented, such that ESD tolerance issignificantly improved.

(2.7) Third Modification of Second Embodiment

An acoustic wave device 1 e according to a third modification of thesecond preferred embodiment shown in FIG. 15 differs from the acousticwave device 1 d in that the length of the outer busbar portion 51 of theleft-side second interdigital transducer electrode 3B is greater thanthat in the acoustic wave device 1 d according to the secondmodification of the second preferred embodiment. The other features ofthe acoustic wave device 1 e according to the third modification are thesame as or similar to that of the acoustic wave device 1 d according tothe second modification of the second preferred embodiment, so thedrawings and description thereof are omitted.

In the acoustic wave device 1 e, a side, closer to the firstinterdigital transducer electrode 3A, of the outer busbar portion 51 ofthe left-side second interdigital transducer electrode 3B and a side,closer to the second electrode finger 7, of the wide portion 62 of thefirst electrode finger 6 closest to the first interdigital transducerelectrode 3A of the above-described group of electrode fingers of theleft-side second interdigital transducer electrode 3B are aligned in astraight line or substantially in a straight line in the first directionD1.

With the acoustic wave device 1 e according to the third modification,the length of the outer busbar portion 51 of the left-side secondinterdigital transducer electrode 3B is increased as compared to theacoustic wave device 1 d according to the second modification, such thatinterference with a piston mode is significantly reduced or prevented.

(2.8) Fourth Modification of Second Embodiment

As shown in FIG. 16, in an acoustic wave device 1 f according to afourth modification of the second preferred embodiment, a multilayerboard 2 f includes a high acoustic velocity film 22, the low acousticvelocity film 23, and the piezoelectric body portion 24. The highacoustic velocity film 22 is provided on or above the support substrate20. Here, the state “provided on or above the support substrate 20”includes the case of being directly provided on the support substrate 20and the case of being indirectly provided on the support substrate 20.In the high acoustic velocity film 22, bulk waves propagate at a higheracoustic velocity than acoustic waves that propagate through thepiezoelectric body portion (piezoelectric film) 24. The low acousticvelocity film 23 is provided on or above the high acoustic velocity film22. Here, the state “provided on or above the high acoustic velocityfilm 22” includes the case of being directly provided on the highacoustic velocity film 22 and the case of being indirectly provided onthe high acoustic velocity film 22. In the low acoustic velocity film23, bulk waves propagate at a lower acoustic velocity than acousticwaves that propagate through the piezoelectric body portion 24. Thepiezoelectric body portion 24 is provided on or above the low acousticvelocity film 23. Here, the state “provided on or above the low acousticvelocity film 23” includes the case of being directly provided on thelow acoustic velocity film 23 and the case of being indirectly providedon the low acoustic velocity film 23. As for the acoustic wave device 1f according to the fourth modification, like reference numerals denotesimilar components to those of the acoustic wave device 1 b (see FIG. 7to FIG. 11) according to the second preferred embodiment, and thedescription thereof is omitted.

The support substrate 20 may include a piezoelectric body, for example,sapphire, lithium tantalate, lithium niobate, and quartz crystal,various ceramics, for example, alumina, magnesia, silicon nitride,aluminum nitride, silicon carbide, zirconia, cordierite, mullite,steatite, and forsterite, a dielectric, for example, glass, or asemiconductor, for example, silicon and gallium nitride, a resinsubstrate, or the like.

In the acoustic wave device 1 f according to the fourth modification,the high acoustic velocity film 22 significantly reduces or preventsacoustic waves from leaking to the structure below the high acousticvelocity film 22.

In the acoustic wave device 1 f according to the fourth modification,the energy of acoustic waves in a specific mode that provides thecharacteristics of a filter or resonator is distributed all over thepiezoelectric body portion 24 and the low acoustic velocity film 23, theenergy is also distributed to a portion, closer to the low acousticvelocity film 23, of the high acoustic velocity film 22, and the energyis not distributed to the high acoustic velocity support substrate 21.Enclosing acoustic waves with the high acoustic velocity film 22 issimilar to the case of enclosing surface acoustic waves of a Love wavetype that is non-leaking SH (shear horizontal) waves and is, forexample, described in Document “Introduction to surface acoustic wavedevice simulation technology”, Kenya HASHIMOTO, published by

Realize Inc., p.26 to p.28. The above-described structure that enclosesacoustic waves differs from a structure that encloses acoustic waveswith Bragg reflector with an acoustic multilayer film.

The high acoustic velocity film 22 is preferably made of any one ofpiezoelectric bodies, for example, diamond-like carbon, aluminumnitride, aluminum oxide, silicon carbide, silicon nitride, silicon,sapphire, lithium tantalate, lithium niobate, and quartz crystal,various ceramics, for example, alumina, zirconia, cordierite, mullite,steatite, and forsterite, magnesia diamond, a material including any oneof the above materials as a main ingredient, and a material including amixture of some of the above materials as a main ingredient.

For the thickness of the high acoustic velocity film 22, since the highacoustic velocity film 22 encloses acoustic waves in the piezoelectricbody portion 24 and the low acoustic velocity film 23, the thickness ofthe high acoustic velocity film 22 is preferably thicker than the lowacoustic velocity film 23, for example.

With the acoustic wave device 1 f according to the fourth modification,as well as the acoustic wave device 1 b (see FIG. 7 to FIG. 11)according to the second preferred embodiment, surge breakdown due to ESDbetween the outer busbar portion 51 of the first interdigital transducerelectrode 3A and the outer busbar portion 51 of the second interdigitaltransducer electrode 3B is significantly reduced or prevented, so ESDtolerance is significantly improved.

(2.9) Fifth Modification of Second Embodiment

As shown in FIG. 17, in an acoustic wave device 1 g according to a fifthmodification of the second preferred embodiment, a piezoelectric bodyportion 24 g includes a piezoelectric substrate, and the high acousticvelocity support substrate 21 and the low acoustic velocity film 23 inthe acoustic wave device 1 b according to the second preferredembodiment are not provided. As for the acoustic wave device 1 gaccording to the fifth modification, like reference numerals denote thesame or similar components to those of the acoustic wave device 1 b (seeFIG. 7 to FIG. 11) according to the second preferred embodiment, and thedescription thereof is omitted.

In the acoustic wave device 1 g, the piezoelectric substrate thatdefines the piezoelectric body portion 24 g is preferably a 128-degreeY-X lithium niobate (LiNbO₃) substrate, for example. The piezoelectricsubstrate is preferably made of, for example, a substrate including a50-degree Y-cut X-propagation lithium tantalate (LiTaO₃) piezoelectricmonocrystal or piezoelectric ceramics (lithium tantalate monocrystal orceramics cut along a plane having an axis rotated by about 50 degreesfrom the Y-axis about the X-axis as the direction of the normal, andthrough which acoustic waves propagate in the X-axis direction).Although not shown in FIG. 17, the acoustic wave device 1 g includes asilicon oxide (SiO₂) film that covers the plurality of (three)interdigital transducer electrodes 3, the two reflectors 8, and a regionnot covered with the plurality of (three) interdigital transducerelectrodes 3 and the two reflectors 8 on one main surface 241 g of thepiezoelectric body portion 24 g. In the acoustic wave device 1 g, thesurface shape of the silicon oxide film has recesses and protrusionscorresponding to the shapes of the three interdigital transducerelectrodes 3 and two reflectors 8.

With the acoustic wave device 1 g according to the fifth modification,as well as the acoustic wave device 1 b (see FIG. 7 to FIG. 11)according to the second preferred embodiment, surge breakdown due to ESDbetween the outer busbar portion 51 of the first interdigital transducerelectrode 3A and the outer busbar portion 51 of the second interdigitaltransducer electrode 3B is significantly reduced or prevented, so ESDtolerance is significantly improved.

(2.10) Other Modifications of Second Embodiment

The number of the plurality of first electrode fingers 6 and the numberof the plurality of second electrode fingers 7 in each of the pluralityof interdigital transducer electrodes 3 are not limited. Here, in thefirst interdigital transducer electrode 3A, the first end electrodefinger and the second end electrode finger respectively located at oneend and the other end in the second direction D2 of the group ofelectrode fingers are not limited to the first electrode fingers 6. Forexample, one of the first end electrode finger and the second endelectrode finger may be the first electrode finger 6, and the other maybe the second electrode finger 7. Accordingly, the inner busbar portion52 of the second busbar 5 is close to the first electrode finger 6 thatis the first end electrode finger, and the inner busbar portion 42 ofthe first busbar 4 is close to the second electrode finger 7 that is thesecond end electrode finger. Each of the first end electrode finger andthe second end electrode finger may be the second electrode finger 7.Accordingly, the inner busbar portion 42 of the first busbar 4 is closeto the second electrode fingers 7 that are respectively the first endelectrode finger and the second end electrode finger. The group ofelectrode fingers only needs to include the plurality of first electrodefingers 6 and the plurality of second electrode fingers 7 spaced apartfrom each other in the second direction D2 perpendicular orsubstantially perpendicular to the first direction D1. For example, inan acoustic wave device of one modification, a region in which the firstelectrode finger 6 and the second electrode finger 7 are provided one byone and spaced apart from each other and a region in which the two firstelectrode fingers 6 or the two second electrode fingers 7 are providedin the second direction D2 may be mixed. In the acoustic wave device 1daccording to the second modification, for the left-side secondinterdigital transducer electrode 3B in FIG. 13 of the two secondinterdigital transducer electrodes 3B, the outer busbar portion 51 ofthe second busbar 5 is located on an inner side in the second directionD2 relative to the inner busbar portion 52 at a side closer to the firstinterdigital transducer electrode 3A. However, the features are notlimited thereto. For example, for the right-side second interdigitaltransducer electrode 3B in FIG. 13, the outer busbar portion 51 of thesecond busbar 5 may be located on an inner side in the second directionD2 relative to the inner busbar portion 52 at a side closer to the firstinterdigital transducer electrode 3A. For the first interdigitaltransducer electrode 3A, the outer busbar portion 51 of the secondbusbar 5 may be located on an inner side in the second direction D2relative to the inner busbar portion 52 at a side closer to at least oneof the two second interdigital transducer electrodes 3B. With theacoustic wave device of any one of these as well, the outer busbarportion 51 is located on an inner side in the second direction D2relative to the inner busbar portion 52, so ESD tolerance issignificantly improved. At least one first electrode finger 6 of theplurality of first electrode fingers 6 in each interdigital transducerelectrode 3 only needs to include the wide portion 62, and at least onesecond electrode finger 7 of the plurality of second electrode fingers 7in each interdigital transducer electrode 3 only needs to include havethe wide portion 72.

The above-described first and second preferred embodiments, and thelike, are each merely one of various preferred embodiments of thepresent invention. The above-described preferred embodiments each may bemodified into various forms according to design, or the like, as long asthe object of the present invention is provided.

For example, in the acoustic wave devices 1, 1 a, 1 b, 1 c, 1 d, 1 e, 1f, 1 g, the interdigital transducer electrode(s) 3 is/are directlyprovided on one main surface 214 of the piezoelectric body portion 24 orone main surface 241 g of the piezoelectric body portion 24 g. However,the present invention is not limited thereto. The interdigitaltransducer electrode(s) 3 may be indirectly provided on one main surface214 of the piezoelectric body portion 24 or one main surface 241 g ofthe piezoelectric body portion 24 g. For example, in the acoustic wavedevices 1, 1 a, 1 b, 1 c, 1 d, 1 e, 1 f, 1 g, the interdigitaltransducer electrode(s) 3 may be provided on one main surface 241 of thepiezoelectric body portion 24 or one main surface 241 g of thepiezoelectric body portion 24 g via a dielectric film.

In the acoustic wave devices 1, 1 a, 1 b, 1 c, 1 d, 1 e, the multilayerboard 2 or multilayer board 2 b may include a film interposed betweenthe low acoustic velocity film 23 and the high acoustic velocity supportsubstrate 21. In the acoustic wave device 1 f, the multilayer board 2 fmay include at least one of a film interposed between the high acousticvelocity film 22 and the support substrate 20 and a film interposedbetween the low acoustic velocity film 23 and the piezoelectric bodyportion 24. In the acoustic wave devices 1, 1 a, 1 b, 1 c, 1 d, 1 e, themultilayer board 2 or multilayer board 2 b may include an acousticimpedance layer instead of the low acoustic velocity film 23 between thepiezoelectric body portion 24 and the high acoustic velocity supportsubstrate 21. The acoustic impedance layer significantly reduces orprevents leakage of acoustic waves excited by the interdigitaltransducer electrode 3 into the high acoustic velocity support substrate21. The acoustic impedance layer has a multilayer structure in which atleast one high acoustic impedance layer having a relatively highacoustic impedance and at least one low acoustic impedance layer havinga relatively low acoustic impedance are laminated in the thicknessdirection of the high acoustic velocity support substrate 21. In theabove-described multilayer structure, a plurality of the high acousticimpedance layers may be provided, and a plurality of the low acousticimpedance layers may be provided. Accordingly, the above-describedmultilayer structure is a structure in which the plurality of highacoustic impedance layers and the plurality of low acoustic impedancelayers are alternately laminated one by one in the thickness directionof the high acoustic velocity support substrate 21.

The high acoustic impedance layer is preferably made of, for example,platinum, tungsten, aluminum nitride, lithium tantalate, sapphire,lithium niobate, silicon nitride, or zinc oxide.

The low acoustic impedance layer is preferably made of, for example,silicon oxide, aluminum, or titanium.

The structure including the plurality of interdigital transducerelectrodes 3 is not limited to the longitudinally coupled resonatorfilter and may be, for example, transversely coupled resonator-typefilter, a ladder filter, or the like.

From the above-described preferred embodiments, and the like, thefollowing features are provided.

An acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1 e; 1 f; 1 g) accordingto a preferred embodiment of the present invention includes a firstterminal (11), a second terminal (12), a piezoelectric body portion (24;24 g), an interdigital transducer electrode (3), and a reflector (8).The second terminal (12) has a lower potential than the first terminal(11). The interdigital transducer electrode (3) is provided on or abovethe piezoelectric body portion (24; 24 g) and electrically connected tothe first terminal (11) and the second terminal (12). The reflector (8)is provided on or above the piezoelectric body portion (24; 24 g) andelectrically connected to the second terminal (12). The interdigitaltransducer electrode (3) includes a first busbar (4), a second busbar(5), a plurality of first electrode fingers (6), and a plurality ofsecond electrode fingers (7). The first busbar (4) is electricallyconnected to the first terminal (11). The second busbar (5) is opposedto the first busbar (4) in a first direction (D1) and electricallyconnected to the second terminal (12). The plurality of first electrodefingers (6) are connected to the first busbar (4) and have a greaterwidth from the first busbar (4) toward the second busbar (5) in thefirst direction (D1). The plurality of second electrode fingers (7) areconnected to the second busbar (5) and have a greater width from thesecond busbar (5) toward the first busbar (4) in the first direction(D1). The plurality of first electrode fingers (6) and the plurality ofsecond electrode fingers (7) are spaced apart from each other in asecond direction (D2) perpendicular or substantially perpendicular tothe first direction (D1). At least one electrode finger of the pluralityof first electrode fingers (6) includes a wide portion (62) having agreater width in the second direction (D2) than a center portion (60),in the first direction (D1), of the at least one electrode finger. Atleast one electrode finger of the plurality of second electrode fingers(7) includes a wide portion (72) having a greater width in the seconddirection (D2) than a center portion (70), in the first direction (D1),of the at least one electrode finger. Each of the first busbar (4) andthe second busbar (5) includes an opening portion (40, 50), an innerbusbar portion (42, 52), an outer busbar portion (41, 51), and acoupling portion (43, 53). The inner busbar portion (42, 52) is locatedcloser to the plurality of first electrode fingers (6) and the pluralityof second electrode fingers (7) than the opening portion (40, 50) in thefirst direction (D1). The outer busbar portion (41, 51) is locatedacross the opening portion (40, 50) from the inner busbar portion (42,52) in the first direction (D1). The coupling portion (43, 53) couplesthe inner busbar portion (42, 52) and the outer busbar portion (41, 51)in the first direction (D1). In the interdigital transducer electrode(3), where, of a group of electrode fingers including the plurality offirst electrode fingers (6) and the plurality of second electrodefingers (7), the electrode finger (the second electrode finger 7L or thesecond electrode finger 7R) located at one end in the second direction(D2) is a first end electrode finger and the electrode finger (thesecond electrode finger 7R or the second electrode finger 7L) located atthe other end is a second end electrode finger, the first end electrodefinger is located between the reflector (8) and the second end electrodefinger in the second direction (D2). The outer busbar portion (41) ofone (first busbar 4) of the first busbar (4) and the second busbar (5),not connected to the first end electrode finger (the second electrodefinger 7L or the second electrode finger 7R), is located on an innerside in the second direction (D2) relative to the center portion (70),in the first direction (D1), of the first end electrode finger (thesecond electrode finger 7L or the second electrode finger 7R).

With the above-described acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1e; 1 f; 1 g), ESD tolerance is significantly improved while interferencewith a piston mode is significantly reduced or prevented.

An acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1 e; 1 f; 1 g) accordingto a preferred embodiment of the present invention includes the tworeflectors (8). The two reflectors (8) are provided one by one on bothsides of the interdigital transducer electrode (3) in the seconddirection (D2). The outer busbar portion (41) of one (first busbar 4) ofthe first busbar (4) and the second busbar (5), not connected to thefirst end electrode finger (the second electrode finger 7L or the secondelectrode finger 7R) or the second end electrode finger (the secondelectrode finger 7R or the second electrode finger 7L), is located on aninner side in the second direction (D2) relative to the wide portion(72) of the first end electrode finger (the second electrode finger 7Lor the second electrode finger 7R) and the wide portion (72) of thesecond end electrode finger (the second electrode finger 7R or thesecond electrode finger 7L).

With the above-described acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1e; 1 f; 1 g), surge breakdown is less likely to occur, and ESD tolerancesignificantly improves as compared to when the outer busbar portion (41)of one (first busbar 4) of the first busbar (4) and the second busbar(5), not connected to the first end electrode finger (the secondelectrode finger 7L or the second electrode finger 7R) or the second endelectrode finger (the second electrode finger 7R or the second electrodefinger 7L), overlaps in the first direction (D1) the wide portion (72)of the first end electrode finger (the second electrode finger 7L or thesecond electrode finger 7R) and the wide portion (72) of the second endelectrode finger (the second electrode finger 7R or the second electrodefinger 7L).

An acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1 e; 1 f; 1 g) accordingto a preferred embodiment of the present invention includes the tworeflectors (8). The two reflectors (8) are provided one by one on bothsides of the interdigital transducer electrode (3) in the seconddirection (D2). The outer busbar portion (41) of one (the first busbar4) of the first busbar (4) and the second busbar (5), not connected tothe first end electrode finger (the second electrode finger 7L or thesecond electrode finger 7R) or the second end electrode finger (thesecond electrode finger 7R or the second electrode finger 7L), islocated on an inner side in the second direction (D2) relative to thefirst end electrode finger (the second electrode finger 7L or the secondelectrode finger 7R) and the second end electrode finger (the secondelectrode finger 7R or the second electrode finger 7L) and does notoverlap in the first direction (D1) each of the first end electrodefinger (the second electrode finger 7L or the second electrode finger7R) and the second end electrode finger (the second electrode finger 7Ror the second electrode finger 7L).

With the above-described acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1e; 1 f; 1 g), ESD tolerance is significantly improved.

In an acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1 e; 1 f; 1 g)according to a preferred embodiment of the present invention, one side(the side 42L or the side 42R), along the first direction (D1), of theinner busbar portion (42) of one (the first busbar 4) of the firstbusbar (4) and the second busbar (5), not connected to the first endelectrode finger (the second electrode finger 7L or the second electrodefinger 7R) or the second end electrode finger (the second electrodefinger 7R or the second electrode finger 7L), and a side (the side 72LLor the side 72RR), away from the second end electrode finger (the secondelectrode finger 7R or the second electrode finger 7L), of the wideportion (72) of the first end electrode finger (the second electrodefinger 7L or the second electrode finger 7R) are aligned in a straightline or substantially in a straight line.

With the above-described acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1e; 1 f; 1 g), ESD tolerance is significantly improved by changing onlythe shape of the outer busbar portion (41) of one (the first busbar 4)of the first busbar (4) and the second busbar (5), not connected to thefirst end electrode finger (the second electrode finger 7L or the secondelectrode finger 7R) or the second end electrode finger (the secondelectrode finger 7R or the second electrode finger 7L), without changingthe shape of the inner busbar portion (42) of the busbar (the firstbusbar 4) not connected to the first end electrode finger (the secondelectrode finger 7L or the second electrode finger 7R) or the second endelectrode finger (the second electrode finger 7R or the second electrodefinger 7L), so ESD tolerance is further improved while interference witha piston mode is significantly reduced or prevented.

An acoustic wave device (1 b; 1 c; 1 d; 1 e; 1 f; 1 g) according to apreferred embodiment of the present invention includes a first terminal(11), a second terminal (12), a piezoelectric body portion (24; 24 g), aplurality of interdigital transducer electrodes (3), and two reflectors(8). The second terminal (12) has a lower potential than the firstterminal (11). The plurality of interdigital transducer electrodes (3)are provided on or above the piezoelectric body portion (24; 24 g) andelectrically connected to the first terminal (11) and the secondterminal (12). The two reflectors (8) are provided on or above thepiezoelectric body portion (24; 24 g) and reflect acoustic waves excitedby the plurality of interdigital transducer electrodes (3). Each of theplurality of interdigital transducer electrodes (3) includes a firstbusbar (4), a second busbar (5), a plurality of first electrode fingers(6), and a plurality of second electrode fingers (7). The second busbar(5) is opposed to the first busbar (4) in the first direction (D1). Theplurality of first electrode fingers (6) are connected to the firstbusbar (4) and have a greater width from the first busbar (4) toward thesecond busbar (5) in the first direction (D1). The plurality of secondelectrode fingers (7) are connected to the second busbar (5) and have agreater width from the second busbar (5) toward the first busbar (4) inthe first direction (D1). The plurality of first electrode fingers (6)and the plurality of second electrode fingers (7) are spaced apart fromeach other in a second direction (D2) perpendicular or substantiallyperpendicular to the first direction (D1). At least one electrode fingerof the plurality of first electrode fingers (6) includes a wide portion(62) having a greater width in the second direction (D2) than a centerportion (60), in the first direction (D1), of the at least one electrodefinger. At least one electrode finger of the plurality of secondelectrode fingers (7) includes a wide portion (72) having a greaterwidth in the second direction (D2) than a center portion (70), in thefirst direction (D1), of the at least one electrode finger. Each of thefirst busbar (4) and the second busbar (5) includes an opening portion(40, 50), an inner busbar portion (42, 52), an outer busbar portion (41,51), and a coupling portion (43, 53). The inner busbar portion (42, 52)is located closer to the plurality of first electrode fingers (6) andthe plurality of second electrode fingers (7) than the opening portion(40, 50) in the first direction (D1). The outer busbar portion (41, 51)is located across the opening portion (40, 50) from the inner busbarportion (42, 52) in the first direction (D1). The coupling portion (43,53) couples the inner busbar portion (42, 52) and the outer busbarportion (41, 51) in the first direction (D1). The plurality ofinterdigital transducer electrodes (3) are provided in the seconddirection (D2). The two reflectors (8) each are located across theinterdigital transducer electrode (3) at any one of both sides of theplurality of interdigital transducer electrodes (3) provided in thesecond direction (D2) from the interdigital transducer electrode (3)adjacent to the interdigital transducer electrode (3) at the any one ofboth sides. In the interdigital transducer electrode (3) adjacent to oneof the two reflectors (8) of the plurality of interdigital transducerelectrodes (3), where, of a group of electrode fingers including theplurality of first electrode fingers (6) and the plurality of secondelectrode fingers (7), the electrode finger (the first end electrodefinger 6) located at one end in the second direction (D2) is a first endelectrode finger and the electrode finger (the first electrode finger 6)located at the other end is a second end electrode finger, the first endelectrode finger is located between the one of the two reflectors (8)and the second end electrode finger in the second direction (D2). In theinterdigital transducer electrode (3) adjacent to the one of thereflectors (8), the outer busbar portion (51) of one (the second busbar5) of the first busbar (4) and the second busbar (5), not connected tothe first end electrode finger (the first electrode finger 6), islocated on an inner side in the second direction (D2) relative to acenter portion (60), in the first direction (D1), of the first endelectrode finger (the first electrode finger 6).

With the above-described acoustic wave device (1 b; 1 c; 1 d; 1 e; 1 f;1 g), ESD tolerance is significantly improved while interference with apiston mode is significantly reduced or prevented.

In an acoustic wave device (1 b; 1 c; 1 d; 1 e; 1 f; 1 g) according to apreferred embodiment of the present invention, in the interdigitaltransducer electrode (3) adjacent to the one of the reflectors (8), theouter busbar portion (the outer busbar portion 51) of one (second busbar5) of the first busbar (4) and the second busbar (5), not connected tothe first end electrode finger (first electrode finger 6) or the secondend electrode finger (the first electrode finger 6), is located on aninner side in the second direction (D2) relative to the wide portion(62) of the first end electrode finger (the first electrode finger 6)and the wide portion (62) of the second end electrode finger (the firstelectrode finger 6).

With the above-described acoustic wave device (1 b; 1 c; 1 e; 1 f; 1 g),surge breakdown is less likely to occur, and ESD tolerance significantlyimproves as compared to when, in the interdigital transducer electrode(3) adjacent to the one of the reflectors (8), the outer busbar portion(51) of one (the second busbar 5) of the first busbar (4) and the secondbusbar (5), not connected to the first end electrode finger (the firstelectrode finger 6) or the second end electrode finger (the firstelectrode finger 6), overlaps in the first direction (D1) the wideportion (62) of the first end electrode finger (the first electrodefinger 6) and the wide portion (62) of the second end electrode finger(the first electrode finger 6).

In an acoustic wave device (1 b; 1 c; 1 e; 1 f; 1 g) according to apreferred embodiment of the present invention, in the interdigitaltransducer electrode (3) adjacent to the one of the reflectors (8), theouter busbar portion (51) of one (second busbar 5) of the first busbar(4) and the second busbar (5), not connected to the first end electrodefinger (the first electrode finger 6) or the second end electrode finger(the first electrode finger 6), is located on an inner side in thesecond direction (D2) and does not overlap in the first direction (D1)the first end electrode finger (the first electrode finger 6) or thesecond end electrode finger (the first electrode finger 6).

With the above-described acoustic wave device (1 b; 1 c; 1 e; 1 f; 1 g),ESD tolerance is significantly improved.

In an acoustic wave device according to a preferred embodiment of thepresent invention, in the interdigital transducer electrode (3) adjacentto the one of the reflectors (8), a side, closer to the one of thereflectors (8), of the inner busbar portion (the inner busbar portion52) of one (the second busbar 5) of the first busbar (4) and the secondbusbar (5), not connected to the first end electrode finger (the firstelectrode finger 6) or the second end electrode finger (the firstelectrode finger 6), and a side, closer to the one of the reflectors(8), of the wide portion (62) of the first end electrode finger (thefirst electrode finger 6) are aligned in a straight line orsubstantially in a straight line.

With the above-described acoustic wave device (1 b; 1 c; 1 e; 1 f; 1 g),ESD tolerance is significantly improved by changing only the shape ofthe outer busbar portion (51) of one (the second busbar 5) of the firstbusbar (4) and the second busbar (5), not connected to the first endelectrode finger (the first electrode finger 6) or the second endelectrode finger (the first electrode finger 6), without changing theshape of the inner busbar portion (52) of the one (the second busbar 5)of the first busbar (4) and the second busbar (5), not connected to thefirst end electrode finger (the first electrode finger 6) or the secondend electrode finger (the first electrode finger 6), so ESD tolerance isfurther improved while interference with a piston mode is significantlyreduced or prevented.

An acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1 e; 1 f; 1 g) accordingto a preferred embodiment of the present invention includes a firstterminal (11), a second terminal (12), a piezoelectric body portion (24;24 g), an interdigital transducer electrode (3), and a reflector (8).The second terminal (12) has a lower potential than the first terminal(11). The interdigital transducer electrode (3) is provided on or abovethe piezoelectric body portion (24; 24 g) and electrically connected tothe first terminal (11) and the second terminal (12). The reflector (8)is provided on or above the piezoelectric body portion (24; 24 g) andelectrically connected to the second terminal (12). The interdigitaltransducer electrode (3) includes a first busbar (4), a second busbar(5), a plurality of first electrode fingers (6), and a plurality ofsecond electrode fingers (7). The first busbar (4) is electricallyconnected to the first terminal (11). The second busbar (5) is opposedto the first busbar (4) in a first direction (D1) and electricallyconnected to the second terminal (12). The plurality of first electrodefingers (6) are connected to the first busbar (4) and have a greaterwidth from the first busbar (4) toward the second busbar (5) in thefirst direction (D1). The plurality of second electrode fingers (7) areconnected to the second busbar (5) and have a greater width from thesecond busbar (5) toward the first busbar (4) in the first direction(D1). The plurality of first electrode fingers (6) and the plurality ofsecond electrode fingers (7) are spaced apart from each other in asecond direction (D2) perpendicular or substantially perpendicular tothe first direction (D1). At least one electrode finger of the pluralityof first electrode fingers (6) includes a wide portion (62) having agreater width in the second direction (D2) than a center portion (60),in the first direction (D1), of the at least one electrode finger. Atleast one electrode finger of the plurality of second electrode fingers(7) includes a wide portion (72) having a greater width in the seconddirection (D2) than a center portion (70), in the first direction (D1),of the at least one electrode finger. Each of the first busbar (4) andthe second busbar (5) includes an opening portion (40, 50), an innerbusbar portion (42, 52), an outer busbar portion (41, 51), and acoupling portion (43, 53). The inner busbar portion (42, 52) is locatedcloser to the plurality of first electrode fingers (6) and the pluralityof second electrode fingers (7) than the opening portion (40, 50) in thefirst direction (D1). The outer busbar portion (41, 51) is locatedacross the opening portion (40, 50) from the inner busbar portion (42,52) in the first direction (D1). The coupling portion (43, 53) couplesthe inner busbar portion (42, 52) and the outer busbar portion (41, 51)in the first direction (D1). In the interdigital transducer electrode(3), where, of a group of electrode fingers including the plurality offirst electrode fingers (6) and the plurality of second electrodefingers (7), the electrode finger (the second electrode finger 7L or thesecond electrode finger 7R) located at one end in the second direction(D2) is a first end electrode finger and the electrode finger (thesecond electrode finger 7R or the second electrode finger 7L) located atthe other end is a second end electrode finger, the first end electrodefinger is located between the reflector (8) and the second end electrodefinger in the second direction (D2). The outer busbar portion (41) ofone (first busbar 4) of the first busbar (4) and the second busbar (5),not connected to the first end electrode finger (the second electrodefinger 7L or the second electrode finger 7R), is located on an innerside in the second direction (D2) relative to the inner busbar portion(42) of the busbar (the first busbar 4) not connected to the first endelectrode finger (the second electrode finger 7L or the second electrodefinger 7R).

With the above-described acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1e; 1 f; 1 g), ESD tolerance is significantly improved while interferencewith a piston mode is significantly reduced or prevented.

An acoustic wave device (1 b; 1 c; 1 d; 1 e; 1 f; 1 g) according to apreferred embodiment of the present invention includes a first terminal(11), a second terminal (12), a piezoelectric body portion (24; 24 g), aplurality of interdigital transducer electrodes (3), and two reflectors(8). The second terminal (12) has a lower potential than the firstterminal (11). The plurality of interdigital transducer electrodes (3)are provided on or above the piezoelectric body portion (24; 24 g) andelectrically connected to the first terminal (11) and the secondterminal (12). The two reflectors (8) are provided on or above thepiezoelectric body portion (24; 24 g) and reflect acoustic waves excitedby the plurality of interdigital transducer electrodes (3). Each of theplurality of interdigital transducer electrodes (3) includes a firstbusbar (4), a second busbar (5), a plurality of first electrode fingers(6), and a plurality of second electrode fingers (7). The second busbar(5) is opposed to the first busbar (4) in the first direction (D1). Theplurality of first electrode fingers (6) are connected to the firstbusbar (4) and have a greater width from the first busbar (4) toward thesecond busbar (5) in the first direction (D1). The plurality of secondelectrode fingers (7) are connected to the second busbar (5) and have agreater width from the second busbar (5) toward the first busbar (4) inthe first direction (D1). The plurality of first electrode fingers (6)and the plurality of second electrode fingers (7) are spaced apart fromeach other in a second direction (D2) perpendicular or substantiallyperpendicular to the first direction (D1). At least one electrode fingerof the plurality of first electrode fingers (6) includes a wide portion(62) having a greater width in the second direction (D2) than a centerportion (60), in the first direction (D1), of the at least one electrodefinger. At least one electrode finger of the plurality of secondelectrode fingers (7) includes a wide portion (72) having a greaterwidth in the second direction (D2) than a center portion (70), in thefirst direction (D1), of the at least one electrode finger. Each of thefirst busbar (4) and the second busbar (5) includes an opening portion(40, 50), an inner busbar portion (42, 52), an outer busbar portion (41,51), and a coupling portion (43, 53). The inner busbar portion (42, 52)is located closer to the plurality of first electrode fingers (6) andthe plurality of second electrode fingers (7) than the opening portion(40, 50) in the first direction (D1). The outer busbar portion (41, 51)is located across the opening portion (40, 50) from the inner busbarportion (42, 52) in the first direction (D1). The coupling portion (43,53) couples the inner busbar portion (42, 52) and the outer busbarportion (41, 51) in the first direction (D1). The plurality ofinterdigital transducer electrodes (3) is provided in the seconddirection (D2). The two reflectors (8) each are located across theinterdigital transducer electrode (3) at any one of both sides of theplurality of interdigital transducer electrodes (3) provided in thesecond direction (D2) from the interdigital transducer electrode (3)adjacent to the interdigital transducer electrode (3) at the any one ofboth sides. In the interdigital transducer electrode (3) adjacent to oneof the two reflectors (8) of the plurality of interdigital transducerelectrodes (3), where, of a group of electrode fingers including theplurality of first electrode fingers (6) and the plurality of secondelectrode fingers (7), the electrode finger (the first end electrodefinger 6) located at one end in the second direction (D2) is a first endelectrode finger and the electrode finger (the first electrode finger 6)located at another end is a second end electrode finger, the first endelectrode finger (the first electrode finger 6) is located between theone of the reflectors (8) and the second end electrode finger (the firstelectrode finger 6) in the second direction (D2). In the interdigitaltransducer electrode (3) adjacent to the one of the reflectors (8), theouter busbar portion (51) of one (the second busbar 5) of the firstbusbar (4) and the second busbar (5), not connected to the first endelectrode finger (the first electrode finger 6), is located on an innerside in the second direction (D2) relative to the inner busbar portion(52) of the busbar (the second busbar) not connected to the first endelectrode finger (the first electrode finger 6).

With the above-described acoustic wave device (1 b; 1 c; 1 d; 1 e; 1 f;1 g) according to the tenth aspect, ESD tolerance is significantlyimproved while interference with a piston mode is significantly reducedor prevented.

An acoustic wave device (1 b; 1 c; 1 d; 1 e; 1 f; 1 g) according to apreferred embodiment of the present invention includes a first terminal(11), a second terminal (12), a piezoelectric body portion (24; 24 g),and a plurality of interdigital transducer electrodes (3). The secondterminal (12) has a lower potential than the first terminal (11). Theplurality of interdigital transducer electrodes (3) are provided on orabove the piezoelectric body portion (24; 24 g) and electricallyconnected to the first terminal (11) and the second terminal (12). Eachof the plurality of interdigital transducer electrodes (3) includes afirst busbar (4), a second busbar (5), a plurality of first electrodefingers (6), and a plurality of second electrode fingers (7). The secondbusbar (5) is opposed to the first busbar (4) in the first direction(D1). The plurality of first electrode fingers (6) are connected to thefirst busbar (4) and have a greater width from the first busbar (4)toward the second busbar (5) in the first direction (D1). The pluralityof second electrode fingers (7) are connected to the second busbar (5)and have a greater width from the second busbar (5) toward the firstbusbar (4) in the first direction (D1). The plurality of first electrodefingers (6) and the plurality of second electrode fingers (7) are spacedapart from each other in a second direction (D2) perpendicular orsubstantially perpendicular to the first direction (D1). At least oneelectrode finger of the plurality of first electrode fingers (6)includes a wide portion (62) having a greater width in the seconddirection (D2) than a center portion (60), in the first direction (D1),of the at least one electrode finger. At least one electrode finger ofthe plurality of second electrode fingers (7) includes a wide portion(72) having a greater width in the second direction (D2) than a centerportion (70), in the first direction (D1), of the at least one electrodefinger. Each of the first busbar (4) and the second busbar (5) includesan opening portion (40, 50), an inner busbar portion (42, 52), an outerbusbar portion (41, 51), and a coupling portion (43, 53). The innerbusbar portion (42, 52) is located closer to the plurality of firstelectrode fingers (6) and the plurality of second electrode fingers (7)than the opening portion (40, 50) in the first direction (D1). The outerbusbar portion (41, 51) is located across the opening portion (40, 50)from the inner busbar portion (42, 52) in the first direction (D1). Thecoupling portion (43, 53) couples the inner busbar portion (42, 52) andthe outer busbar portion (41, 51) in the first direction (D1). Where, ofthe plurality of interdigital transducer electrodes (3), one of theadjacent two interdigital transducer electrodes (3) in the seconddirection (D2) is a first interdigital transducer electrode (3A) andanother one is a second interdigital transducer electrode (3B), adistance between the outer busbar portion (51) not connected to, of agroup of electrode fingers including the plurality of first electrodefingers (6) and the plurality of second electrode fingers (7), theelectrode finger closest to the second interdigital transducer electrode(3B) in the first interdigital transducer electrode (3A) and the outerbusbar portion (51) not connected to, of a group of electrode fingersincluding the plurality of first electrode fingers (6) and the pluralityof second electrode fingers (7), the electrode finger closest to thefirst interdigital transducer electrode (3A) in the second interdigitaltransducer electrode (3B) is greater than a distance between a centerportion (60) of the electrode finger (the first electrode finger 6)closest to the second interdigital transducer electrode (3B) in thefirst interdigital transducer electrode (3A) and a center portion (60)of the electrode finger (the first electrode finger 6) closest to thefirst interdigital transducer electrode (3A) in the second interdigitaltransducer electrode (3B).

With the above-described acoustic wave device (1 b; 1 c; 1 d; 1 e; 1 f;1 g) according to the eleventh aspect, ESD tolerance is significantlyimproved while interference with a piston mode is significantly reducedor prevented.

An acoustic wave device (1 b; 1 c; 1 f; 1 g) according to a preferredembodiment of the present invention includes a first terminal (12), asecond terminal (12), a piezoelectric body portion (24; 24 g), and aplurality of interdigital transducer electrodes (3). The second terminal(12) has a lower potential than the first terminal (11). The pluralityof interdigital transducer electrodes (3) are provided on or above thepiezoelectric body portion (24; 24 g) and electrically connected to thefirst terminal (11) and the second terminal (12). Each of the pluralityof interdigital transducer electrodes (3) includes a first busbar (4), asecond busbar (5), a plurality of first electrode fingers (6), and aplurality of second electrode fingers (7). The second busbar (5) isopposed to the first busbar (4) in the first direction (D1). Theplurality of first electrode fingers (6) are connected to the firstbusbar (4) and have a greater width from the first busbar (4) toward thesecond busbar (5) in the first direction (D1). The plurality of secondelectrode fingers (7) are connected to the second busbar (5) and have agreater width from the second busbar (5) toward the first busbar (4) inthe first direction (D1). The plurality of first electrode fingers (6)and the plurality of second electrode fingers (7) are spaced apart fromeach other in a second direction (D2) perpendicular or substantiallyperpendicular to the first direction (D1). At least one electrode fingerof the plurality of first electrode fingers (6) includes a wide portion(62) having a greater width in the second direction (D2) than a centerportion (60), in the first direction (D1), of the at least one electrodefinger. At least one electrode finger of the plurality of secondelectrode fingers (7) includes a wide portion (72) having a greaterwidth in the second direction (D2) than a center portion (70), in thefirst direction (D1), of the at least one electrode finger. Each of thefirst busbar (4) and the second busbar (5) includes an opening portion(40, 50), an inner busbar portion (42, 52), an outer busbar portion (41,51), and a coupling portion (43, 53). The inner busbar portion (42, 52)is located closer to the plurality of first electrode fingers (6) andthe plurality of second electrode fingers (7) than the opening portion(40, 50) in the first direction (D1). The outer busbar portion (41, 51)is located across the opening portion (40, 50) from the inner busbarportion (42, 52) in the first direction (D1). The coupling portion (43,53) couples the inner busbar portion (42, 52) and the outer busbarportion (41, 51) in the first direction (D1). Where, of the plurality ofinterdigital transducer electrodes (3), one of the adjacent twointerdigital transducer electrodes (3) in the second direction (D2) is afirst interdigital transducer electrode (3A) and another is a secondinterdigital transducer electrode (3B), and where, of a group ofelectrode fingers including the plurality of first electrode fingers (6)and the plurality of second electrode fingers (7) of the firstinterdigital transducer electrode (3A), the electrode finger (the firstend electrode finger 6) located at an end closer to the secondinterdigital transducer electrode (3B) in the second direction (D2) is afirst end electrode finger of the first interdigital transducerelectrode (3A), the electrode finger (the first electrode finger 6)located at an end away from the second interdigital transducer electrode(3B) is a second end electrode finger of the first interdigitaltransducer electrode (3A), and, of a group of electrode fingersincluding the plurality of first electrode fingers (6) and the pluralityof second electrode fingers (7) of the second interdigital transducerelectrode (3B), the electrode finger (the first electrode finger 6)located at an end closer to the first interdigital transducer electrode(3A) in the second direction (D2) is a first end electrode finger of thesecond interdigital transducer electrode (3B) and the electrode finger(the first electrode finger 6) located at an end away from the firstinterdigital transducer electrode (3A) is a second end electrode fingerof the second interdigital transducer electrode (3B), the first endelectrode finger of the first interdigital transducer electrode (3A) isconnected to the first terminal (11), and the first end electrode fingerof the second interdigital transducer electrode (3B) is connected to thesecond terminal (12). In each of the first interdigital transducerelectrode (3A) and the second interdigital transducer electrode (3B),the outer busbar portion (51) electrically connected to one of the firstterminal (11) and the second terminal (12), different from the terminalto which the first end electrode finger is connected, is located on aninner side in the second direction (D2) relative to the inner busbarportion (52) electrically connected to the one of the first terminal(11) and the second terminal (12), different from the terminal to whichthe first end electrode finger is connected.

With the above-described acoustic wave device (1 b; 1 c; 1 f; 1 g), ESDtolerance is significantly improved while interference with a pistonmode is significantly reduced or prevented.

An acoustic wave device (1 b; 1 c; 1 d; 1 e; 1 f; 1 g) according to apreferred embodiment of the present invention includes a first terminal(11), a second terminal (12), a piezoelectric body portion (24; 24 g),and a plurality of interdigital transducer electrodes (3). The secondterminal (12) has a lower potential than the first terminal (11). Theplurality of interdigital transducer electrodes (3) are provided on orabove the piezoelectric body portion (24; 24 g) and electricallyconnected to the first terminal (11) and the second terminal (12). Eachof the plurality of interdigital transducer electrodes (3) includes afirst busbar (4), a second busbar (5), a plurality of first electrodefingers (6), and a plurality of second electrode fingers (7). The secondbusbar (5) is opposed to the first busbar (4) in the first direction(D1). The plurality of first electrode fingers (6) are connected to thefirst busbar (4) and have a greater width from the first busbar (4)toward the second busbar (5) in the first direction (D1). The pluralityof second electrode fingers (7) are connected to the second busbar (5)and have a greater width from the second busbar (5) toward the firstbusbar (4) in the first direction (D1). The plurality of first electrodefingers (6) and the plurality of second electrode fingers (7) are spacedapart from each other in a second direction (D2) perpendicular orsubstantially perpendicular to the first direction (D1). At least oneelectrode finger of the plurality of first electrode fingers (6)includes a wide portion (62) having a greater width in the seconddirection (D2) than a center portion (60), in the first direction (D1),of the at least one electrode finger. At least one electrode finger ofthe plurality of second electrode fingers (7) includes a wide portion(72) having a greater width in the second direction (D2) than a centerportion (70), in the first direction (D1), of the at least one electrodefinger. Each of the first busbar (4) and the second busbar (5) includesan opening portion (40, 50), an inner busbar portion (42, 52), an outerbusbar portion (41, 51), and a coupling portion (43, 53). The innerbusbar portion (42, 52) is located closer to the plurality of firstelectrode fingers (6) and the plurality of second electrode fingers (7)than the opening portion (40, 50) in the first direction (D1). The outerbusbar portion (41, 51) is located across the opening portion (40, 50)from the inner busbar portion (42, 52) in the first direction (D1). Thecoupling portion (43, 53) couples the inner busbar portion (42, 52) andthe outer busbar portion (41, 51) in the first direction (D1). In atleast one of the plurality of interdigital transducer electrodes (3),where, of a group of electrode fingers including the plurality of firstelectrode fingers (6) and the plurality of second electrode fingers (7),the electrode finger (the first electrode finger 6) located at one endin the second direction (D2) is a first end electrode finger and theelectrode finger (the first electrode finger 6) located at another endis a second end electrode finger, the first end electrode finger islocated closer to the interdigital transducer electrode (3) adjacent tothe at least one interdigital transducer electrode (3) in the seconddirection (D2). In the at least one interdigital transducer electrode(3), the outer busbar portion (51) of one (the second busbar 5) of thefirst busbar (4) and the second busbar (5), not connected to the firstend electrode finger, is located on an inner side in the seconddirection (D2) relative to the inner busbar portion (52) of the one (thesecond busbar 5) of the first busbar (4) and the second busbar (5), notconnected to the first end electrode finger, at least at a side closerto the adjacent interdigital transducer electrode (3).

With the above described acoustic wave device (1 b; 1 c; 1 d; 1 e; 1 f;1 g), ESD tolerance is significantly improved while interference with apiston mode is significantly reduced or prevented.

In an acoustic wave device (1 b; 1 c; 1 d; 1 e; 1 f; 1 g) according to apreferred embodiment of the present invention, the plurality ofinterdigital transducer electrodes (3) are provided in the seconddirection (D2), and the acoustic wave device further includes tworeflectors (8). The two reflectors (8) each are provided across theinterdigital transducer electrode (3) at any one of both sides of theplurality of interdigital transducer electrodes (3) provided in thesecond direction (D2) one by one on or above the piezoelectric bodyportion (24) from the interdigital transducer electrode (3) adjacent tothe interdigital transducer electrode (3) at the any one of both sides.The two reflectors (8) are reflect acoustic waves excited by theplurality of interdigital transducer electrodes (3).

The above-described acoustic wave device (1 b; 1 c; 1 d; 1 e; 1 f; 1 g)is able to provide a longitudinally coupled resonator filter.

In an acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1 e; 1 f) accordingto a preferred embodiment of the present invention, a distal end portion(61) of at least one of the plurality of first electrode fingers (6)includes a wide portion (62), and a distal end portion (71) of at leastone of the plurality of second electrode fingers (7) includes a wideportion (72).

In an acoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1 e; 1 f; 1 g)according to a preferred embodiment of the present invention, theacoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1 e; 1 f; 1 g) includes aplurality of regions (A1 to A11) different from each other in the firstdirection (D1) in plan view taken in a thickness direction of theacoustic wave device (1; 1 a; 1 b; 1 c; 1 d; 1 e; 1 f; 1 g). Theplurality of regions (A1 to A11) include a center region (the regionA6), two outer busbar regions (the regions A1, A11), two inner busbarregions (the regions A3, A9), two coupling regions (the regions A2,A10), two gap regions (the regions A4, A8), and two wide regions (A7,A5). The center region (the region A6) is located in a center in thefirst direction (D1) and includes center portions (60) of the pluralityof first electrode fingers (6) and center portions (70) of the pluralityof second electrode fingers (7). The two outer busbar regions (theregions A1, A11) respectively include the outer busbar portion (41) ofthe first busbar (4) and the outer busbar portion (51) of the secondbusbar (5). The two inner busbar regions (the regions A3, A9)respectively include the inner busbar portion (42) of the first busbar(4) and the inner busbar portion (52) of the second busbar (5). The twocoupling regions (the regions A2, A10) respectively include the couplingportion (43) and opening portion (40) of the first busbar (4) and thecoupling portion (53) and opening portion (50) of the second busbar (5).The two gap regions (the regions A4, A8) respectively include a gap (31)between the plurality of first electrode fingers (6) and the secondbusbar (5) and a gap (32) between the plurality of second electrodefingers (7) and the first busbar (4). The two wide regions (A7, A5)respectively include the wide portion (62) of at least one electrodefinger (the first electrode finger 6) of the plurality of firstelectrode fingers (6) and the wide portion (72) of at least oneelectrode finger (the second electrode finger 7) of the plurality ofsecond electrode fingers (7). An acoustic velocity of acoustic waves inthe two outer busbar regions (the regions A1, A11) is lower than theacoustic velocity in the center region (the region A6). An acousticvelocity of acoustic waves in the two inner busbar regions (the regionsA3, A9) is lower than the acoustic velocity in the center region (theregion A6). An acoustic velocity of acoustic waves in the two couplingregions (the regions A2, A10) is higher than the acoustic velocity inthe two outer busbar regions (the regions A1, A11) or the acousticvelocity in the center region (the region A6). An acoustic velocity ofacoustic waves in the two gap regions (the regions A4, A8) is higherthan the acoustic velocity in the two inner busbar regions (the regionsA3, A9) or the acoustic velocity in the center region (the region A6).An acoustic velocity of acoustic waves in the two wide regions (A7, A5)is lower than the acoustic velocity in the center region (the regionA6).

What is claimed is:
 1. An acoustic wave device comprising: a firstterminal; a second terminal having a lower potential than the firstterminal; a piezoelectric body portion; an interdigital transducerelectrode provided on or above the piezoelectric body portion andelectrically connected to the first terminal and the second terminal;and a reflector provided on or above the piezoelectric body portion andelectrically connected to the second terminal; wherein the interdigitaltransducer electrode includes: a first busbar electrically connected tothe first terminal; a second busbar opposed to the first busbar in afirst direction and electrically connected to the second terminal; aplurality of first electrode fingers connected to the first busbar andhaving a greater width from the first busbar toward the second busbar inthe first direction; and a plurality of second electrode fingersconnected to the second busbar and having a greater width from thesecond busbar toward the first busbar in the first direction; theplurality of first electrode fingers and the plurality of secondelectrode fingers are spaced apart from each other in a second directionperpendicular or substantially perpendicular to the first direction; atleast one electrode finger of the plurality of first electrode fingersincludes a wide portion having a greater width in the second directionthan a center portion, in the first direction, of the at least oneelectrode finger, and at least one electrode finger of the plurality ofsecond electrode fingers includes a wide portion having a greater widthin the second direction than a center portion, in the first direction,of the at least one electrode finger; each of the first busbar and thesecond busbar includes: an opening portion; an inner busbar portionlocated closer to the plurality of first electrode fingers and theplurality of second electrode fingers than the opening portion in thefirst direction; an outer busbar portion located across the openingportion from the inner busbar portion in the first direction; and acoupling portion coupling the inner busbar portion and the outer busbarportion in the first direction; in the interdigital transducerelectrode, where, of a group of electrode fingers including theplurality of first electrode fingers and the plurality of secondelectrode fingers, the electrode finger located at one end in the seconddirection is a first end electrode finger and the electrode fingerlocated at another end is a second end electrode finger, the first endelectrode finger is located between the reflector and the second endelectrode finger in the second direction; and the outer busbar portionof one of the first busbar and the second busbar, not connected to thefirst end electrode finger, is located on an inner side in the seconddirection relative to a center portion, in the first direction, of thefirst end electrode finger.
 2. The acoustic wave device according toclaim 1, wherein the acoustic wave device includes the two reflectors;the two reflectors are provided one by one on both sides of theinterdigital transducer electrode in the second direction; and the outerbusbar portion of one of the first busbar and the second busbar, notconnected to the first end electrode finger or the second end electrodefinger, is located on an inner side in the second direction relative tothe wide portion of the first end electrode finger and the wide portionof the second end electrode finger.
 3. The acoustic wave deviceaccording to claim 1, wherein the acoustic wave device includes the tworeflectors; the two reflectors are provided one by one on both sides ofthe interdigital transducer electrode in the second direction; and theouter busbar portion of one of the first busbar and the second busbar,not connected to the first end electrode finger or the second endelectrode finger, is located on an inner side in the second directionrelative to the first end electrode finger and the second end electrodefinger and does not overlap the first end electrode finger or the secondend electrode finger in the first direction.
 4. The acoustic wave deviceaccording to claim 3, wherein one side, along the first direction, ofthe inner busbar portion of one of the first busbar and the secondbusbar, not connected to the first end electrode finger or the secondend electrode finger, and a side, away from the second end electrodefinger, of the wide portion of the first end electrode finger arealigned in a straight line or substantially in a straight line.
 5. Anacoustic wave device comprising: a first terminal; a second terminallower in potential than the first terminal; a piezoelectric bodyportion; a plurality of interdigital transducer electrodes provided onor above the piezoelectric body portion and electrically connected tothe first terminal and the second terminal; and two reflectors providedon or above the piezoelectric body portion and reflect acoustic wavesexcited by the plurality of interdigital transducer electrodes; whereineach of the plurality of interdigital transducer electrodes includes: afirst busbar; a second busbar opposed to the first busbar in a firstdirection; a plurality of first electrode fingers connected to the firstbusbar and having a greater width from the first busbar toward thesecond busbar in the first direction; and a plurality of secondelectrode fingers connected to the second busbar and having a greaterwidth from the second busbar toward the first busbar in the firstdirection; the plurality of first electrode fingers and the plurality ofsecond electrode fingers are spaced apart in a second directionperpendicular or substantially perpendicular to the first direction; atleast one electrode finger of the plurality of first electrode fingersincludes a wide portion having a greater width in the second directionthan a center portion, in the first direction, of the at least oneelectrode finger, and at least one electrode finger of the plurality ofsecond electrode fingers includes a wide portion having a greater widthin the second direction than a center portion, in the first direction,of the at least one electrode finger; each of the first busbar and thesecond busbar includes: an opening portion; an inner busbar portionlocated closer to the plurality of first electrode fingers and theplurality of second electrode fingers than the opening portion in thefirst direction; an outer busbar portion located across the openingportion from the inner busbar portion in the first direction; and acoupling portion coupling the inner busbar portion and the outer busbarportion in the first direction; the plurality of interdigital transducerelectrodes are arranged in the second direction; the two reflectors eachare located across the interdigital transducer electrode at any one ofboth sides of the plurality of interdigital transducer electrodesarranged in the second direction from the interdigital transducerelectrode adjacent to the interdigital transducer electrode at the anyone of both sides; in the interdigital transducer electrode adjacent toone of the two reflectors, of the plurality of interdigital transducerelectrodes, where, of a group of electrode fingers including theplurality of first electrode fingers and the plurality of secondelectrode fingers, the electrode finger located at one end in the seconddirection is a first end electrode finger and the electrode fingerlocated at another end is a second end electrode finger, the first endelectrode finger is located between the one of the two reflectors andthe second end electrode finger in the second direction; and in theinterdigital transducer electrode adjacent to the one of the tworeflectors, the outer busbar portion of one of the first busbar and thesecond busbar, not connected to the first end electrode finger, islocated on an inner side in the second direction relative to a centerportion, in the first direction, of the first end electrode finger. 6.The acoustic wave device according to claim 5, wherein in theinterdigital transducer electrode adjacent to the one of the tworeflectors, the outer busbar portion of one of the first busbar and thesecond busbar, not connected to the first end electrode finger or thesecond end electrode finger, is located on an inner side in the seconddirection relative to the wide portion of each of the first endelectrode finger and the second end electrode finger.
 7. The acousticwave device according to claim 5, wherein in the interdigital transducerelectrode adjacent to the one of the two reflectors, the outer busbarportion of one of the first busbar and the second busbar, not connectedto the first end electrode finger or the second end electrode finger, islocated on an inner side in the second direction and does not overlapthe first end electrode finger or the second end electrode finger in thefirst direction.
 8. The acoustic wave device according to claim 7,wherein in the interdigital transducer electrode adjacent to the one ofthe reflectors, a side, adjacent to the one of the two reflectors, ofthe inner busbar portion of one of the first busbar and the secondbusbar, not connected to the first end electrode finger or the secondend electrode finger, and a side, adjacent to the one of the tworeflectors, of the wide portion of the first end electrode finger arealigned in a straight line or substantially in a straight line.
 9. Anacoustic wave device comprising: a first terminal; a second terminallower in potential than the first terminal; a piezoelectric bodyportion; an interdigital transducer electrode provided on or above thepiezoelectric body portion and electrically connected to the firstterminal and the second terminal; and a reflector provided on or abovethe piezoelectric body portion and electrically connected to the secondterminal; wherein the interdigital transducer electrode includes: afirst busbar electrically connected to the first terminal; a secondbusbar opposed to the first busbar in a first direction and electricallyconnected to the second terminal; a plurality of first electrode fingersconnected to the first busbar and having a greater width from the firstbusbar toward the second busbar in the first direction; and a pluralityof second electrode fingers connected to the second busbar and having agreater width from the second busbar toward the first busbar in thefirst direction; the plurality of first electrode fingers and theplurality of second electrode fingers are spaced apart from each otherin a second direction perpendicular or substantially perpendicular tothe first direction; at least one electrode finger of the plurality offirst electrode fingers includes a wide portion having a greater widthin the second direction than a center portion, in the first direction,of the at least one electrode finger, and at least one electrode fingerof the plurality of second electrode fingers includes a wide portionhaving a greater width in the second direction than a center portion, inthe first direction, of the at least one electrode finger; each of thefirst busbar and the second busbar includes: an opening portion; aninner busbar portion located closer to the plurality of first electrodefingers and the plurality of second electrode fingers than the openingportion in the first direction; an outer busbar portion located acrossthe opening portion from the inner busbar portion in the firstdirection; and a coupling portion coupling the inner busbar portion andthe outer busbar portion in the first direction; in the interdigitaltransducer electrode, where, of a group of electrode fingers includingthe plurality of first electrode fingers and the plurality of secondelectrode fingers, the electrode finger located at one end in the seconddirection is a first end electrode finger and the electrode fingerlocated at another end is a second end electrode finger, the first endelectrode finger is located between the reflector and the second endelectrode finger in the second direction; and the outer busbar portionof one of the first busbar and the second busbar, not connected to thefirst end electrode finger, is located on an inner side in the seconddirection relative to the inner busbar portion of the busbar notconnected to the first end electrode finger.
 10. An acoustic wave devicecomprising: a first terminal; a second terminal lower in potential thanthe first terminal; a piezoelectric body portion; a plurality ofinterdigital transducer electrodes provided on or above thepiezoelectric body portion and electrically connected to the firstterminal and the second terminal; and two reflectors provided on orabove the piezoelectric body portion and reflect acoustic waves excitedby the plurality of interdigital transducer electrodes; wherein each ofthe plurality of interdigital transducer electrodes includes: a firstbusbar; a second busbar opposed to the first busbar in a firstdirection; a plurality of first electrode fingers connected to the firstbusbar and having a greater width from the first busbar toward thesecond busbar in the first direction; and a plurality of secondelectrode fingers connected to the second busbar and having a greaterwidth from the second busbar toward the first busbar in the firstdirection; the plurality of first electrode fingers and the plurality ofsecond electrode fingers are spaced apart from each other in a seconddirection perpendicular or substantially perpendicular to the firstdirection; at least one electrode finger of the plurality of firstelectrode fingers includes a wide portion having a greater width in thesecond direction than a center portion, in the first direction, of theat least one electrode finger, and at least one electrode finger of theplurality of second electrode fingers includes a wide portion having agreater width in the second direction than a center portion, in thefirst direction, of the at least one electrode finger; each of the firstbusbar and the second busbar includes: an opening portion; an innerbusbar portion located closer to the plurality of first electrodefingers and the plurality of second electrode fingers than the openingportion in the first direction; an outer busbar portion located acrossthe opening portion from the inner busbar portion in the firstdirection; and a coupling portion coupling the inner busbar portion andthe outer busbar portion in the first direction; the plurality ofinterdigital transducer electrodes are arranged in the second direction;the two reflectors each are located across the interdigital transducerelectrode at any one of both sides of the plurality of interdigitaltransducer electrodes arranged in the second direction from theinterdigital transducer electrode adjacent to the interdigitaltransducer electrode at the any one of both sides; in the interdigitaltransducer electrode adjacent to one of the two reflectors, of theplurality of interdigital transducer electrodes, where, of a group ofelectrode fingers including the plurality of first electrode fingers andthe plurality of second electrode fingers, the electrode finger locatedat one end in the second direction is a first end electrode finger andthe electrode finger located at another end is a second end electrodefinger, the first end electrode finger is located between the one of thetwo reflectors and the second end electrode finger in the seconddirection; and in the interdigital transducer electrode adjacent to theone of the two reflectors, the outer busbar portion of one of the firstbusbar and the second busbar, not connected to the first end electrodefinger, is located on an inner side in the second direction relative tothe inner busbar portion of the busbar not connected to the first endelectrode finger.
 11. An acoustic wave device comprising: a firstterminal; a second terminal lower in potential than the first terminal;a piezoelectric body portion; and a plurality of interdigital transducerelectrodes provided on or above the piezoelectric body portion andelectrically connected to the first terminal and the second terminal;wherein each of the plurality of interdigital transducer electrodesincludes: a first busbar; a second busbar opposed to the first busbar ina first direction; a plurality of first electrode fingers connected tothe first busbar and having a greater width from the first busbar towardthe second busbar in the first direction; and a plurality of secondelectrode fingers connected to the second busbar and having a greaterwidth from the second busbar toward the first busbar in the firstdirection; the plurality of first electrode fingers and the plurality ofsecond electrode fingers are spaced apart from each other in a seconddirection perpendicular or substantially perpendicular to the firstdirection; at least one electrode finger of the plurality of firstelectrode fingers includes a wide portion having a greater width in thesecond direction than a center portion, in the first direction, of theat least one electrode finger, and at least one electrode finger of theplurality of second electrode fingers includes a wide portion having agreater width in the second direction than a center portion, in thefirst direction, of the at least one electrode finger; each of the firstbusbar and the second busbar includes: an opening portion; an innerbusbar portion located closer to the plurality of first electrodefingers and the plurality of second electrode fingers than the openingportion in the first direction; an outer busbar portion located acrossthe opening portion from the inner busbar portion in the firstdirection; and a coupling portion coupling the inner busbar portion andthe outer busbar portion in the first direction; where, of the pluralityof interdigital transducer electrodes, one of the two interdigitaltransducer electrodes adjacent to each other in the second direction isa first interdigital transducer electrode and another one of the twointerdigital transducer electrodes is a second interdigital transducerelectrode; and a distance between the outer busbar portion not connectedto, of a group of electrode fingers including the plurality of firstelectrode fingers and the plurality of second electrode fingers, theelectrode finger closest to the second interdigital transducer electrodein the first interdigital transducer electrode and the outer busbarportion not connected to, of a group of electrode fingers including theplurality of first electrode fingers and the plurality of secondelectrode fingers, the electrode finger closest to the firstinterdigital transducer electrode in the second interdigital transducerelectrode is greater than a distance between a center portion of theelectrode finger closest to the second interdigital transducer electrodein the first interdigital transducer electrode and a center portion ofthe electrode finger closest to the first interdigital transducerelectrode in the second interdigital transducer electrode.
 12. Anacoustic wave device comprising: a first terminal; a second terminallower in potential than the first terminal; a piezoelectric bodyportion; and a plurality of interdigital transducer electrodes providedon or above the piezoelectric body portion and electrically connected tothe first terminal and the second terminal; wherein each of theplurality of interdigital transducer electrodes includes: a firstbusbar; a second busbar opposed to the first busbar in a firstdirection; a plurality of first electrode fingers connected to the firstbusbar and having a greater width from the first busbar toward thesecond busbar in the first direction; and a plurality of secondelectrode fingers connected to the second busbar and having a greaterwidth from the second busbar toward the first busbar in the firstdirection; the plurality of first electrode fingers and the plurality ofsecond electrode fingers are spaced apart from each other in a seconddirection perpendicular or substantially perpendicular to the firstdirection; at least one electrode finger of the plurality of firstelectrode fingers includes a wide portion having a greater width in thesecond direction than a center portion, in the first direction, of theat least one electrode finger, and at least one electrode finger of theplurality of second electrode fingers includes a wide portion having agreater width in the second direction than a center portion, in thefirst direction, of the at least one electrode finger; each of the firstbusbar and the second busbar includes: an opening portion; an innerbusbar portion located closer to the plurality of first electrodefingers and the plurality of second electrode fingers than the openingportion in the first direction; an outer busbar portion located acrossthe opening portion from the inner busbar portion in the firstdirection; and a coupling portion coupling the inner busbar portion andthe outer busbar portion in the first direction; where, of the pluralityof interdigital transducer electrodes, one of the two interdigitaltransducer electrodes adjacent to each other in the second direction isa first interdigital transducer electrode and another one of the twointerdigital transducer electrodes is a second interdigital transducerelectrode; where, of a group of electrode fingers including theplurality of first electrode fingers and the plurality of secondelectrode fingers of the first interdigital transducer electrode, theelectrode finger located at an end closer to the second interdigitaltransducer electrode in the second direction is a first end electrodefinger of the first interdigital transducer electrode and the electrodefinger located at an end away from the second interdigital transducerelectrode is a second end electrode finger of the first interdigitaltransducer electrode, and, of a group of electrode fingers including theplurality of first electrode fingers and the plurality of secondelectrode fingers of the second interdigital transducer electrode, theelectrode finger located at an end closer to the first interdigitaltransducer electrode in the second direction is a first end electrodefinger of the second interdigital transducer electrode and the electrodefinger located at an end away from the first interdigital transducerelectrode is a second end electrode finger of the second interdigitaltransducer electrode; the first end electrode finger of the firstinterdigital transducer electrode is connected to the first terminal;the first end electrode finger of the second interdigital transducerelectrode is connected to the second terminal; and in each of the firstinterdigital transducer electrode and the second interdigital transducerelectrode, the outer busbar portion electrically connected to one of thefirst terminal and the second terminal, different from the terminal towhich the first end electrode finger is connected, is located on aninner side in the second direction relative to the inner busbar portionelectrically connected to the one of the first terminal and the secondterminal, different from the terminal to which the first end electrodefinger is connected.
 13. An acoustic wave device comprising: a firstterminal; a second terminal lower in potential than the first terminal;a piezoelectric body portion; and a plurality of interdigital transducerelectrodes provided on or above the piezoelectric body portion andelectrically connected to the first terminal and the second terminal;wherein each of the plurality of interdigital transducer electrodesincludes: a first busbar; a second busbar opposed to the first busbar ina first direction; a plurality of first electrode fingers connected tothe first busbar and having a greater width from the first busbar towardthe second busbar in the first direction; and a plurality of secondelectrode fingers connected to the second busbar and having a greaterwidth from the second busbar toward the first busbar in the firstdirection; the plurality of first electrode fingers and the plurality ofsecond electrode fingers are spaced apart from each other in a seconddirection perpendicular or substantially perpendicular to the firstdirection; at least one electrode finger of the plurality of firstelectrode fingers includes a wide portion having a greater width in thesecond direction than a center portion, in the first direction, of theat least one electrode finger, and at least one electrode finger of theplurality of second electrode fingers includes a wide portion having agreater width in the second direction than a center portion, in thefirst direction, of the at least one electrode finger; each of the firstbusbar and the second busbar includes: an opening portion; an innerbusbar portion located closer to the plurality of first electrodefingers and the plurality of second electrode fingers than the openingportion in the first direction; an outer busbar portion located acrossthe opening portion from the inner busbar portion in the firstdirection; and a coupling portion coupling the inner busbar portion andthe outer busbar portion in the first direction; in at least oneinterdigital transducer electrode of the plurality of interdigitaltransducer electrodes, where, of a group of electrode fingers includingthe plurality of first electrode fingers and the plurality of secondelectrode fingers, the electrode finger located at one end in the seconddirection is a first end electrode finger and the electrode fingerlocated at another end is a second end electrode finger, the first endelectrode finger is located closer to the interdigital transducerelectrode adjacent to the at least one interdigital transducer electrodein the second direction; and in the at least one interdigital transducerelectrode, the outer busbar portion of one of the first busbar and thesecond busbar, not connected to the first end electrode finger, islocated on an inner side in the second direction relative to the innerbusbar portion of one of the first busbar and the second busbar, notconnected to the first end electrode finger, at least at a side closerto the adjacent interdigital transducer electrode.
 14. The acoustic wavedevice according to claim 11, wherein the plurality of interdigitaltransducer electrodes are arranged in the second direction; and theacoustic wave device further includes two reflectors each providedacross the interdigital transducer electrode at any one of both sides ofthe plurality of interdigital transducer electrodes arranged in thesecond direction one by one on or above the piezoelectric body portionfrom the interdigital transducer electrode adjacent to the interdigitaltransducer electrode at the any one of both sides and reflect acousticwaves excited by the plurality of interdigital transducer electrodes.15. The acoustic wave device according to claim 1, wherein a distal endportion of at least one of the plurality of first electrode fingersincludes the wide portion, and a distal end portion of at least one ofthe plurality of second electrode fingers includes the wide portion. 16.The acoustic wave device according to claim 1, wherein the acoustic wavedevice includes a plurality of regions different from each other in thefirst direction in plan view taken in a thickness direction of theacoustic wave device, the plurality of regions include: a center regionlocated in a center in the first direction and including center portionsof the plurality of first electrode fingers and center portions of theplurality of second electrode fingers; two outer busbar regionsrespectively including the outer busbar portion of the first busbar andthe outer busbar portion of the second busbar; two inner busbar regionsrespectively including the inner busbar portion of the first busbar andthe inner busbar portion of the second busbar; two coupling regionsrespectively including the coupling portion and opening portion of thefirst busbar and the coupling portion and opening portion of the secondbusbar; two gap regions respectively including a gap between the secondbusbar and the plurality of first electrode fingers and a gap betweenthe first busbar and the plurality of second electrode fingers; and twowide regions respectively including the wide portion of at least one ofthe plurality of first electrode fingers and the wide portion of atleast one of the plurality of second electrode fingers; an acousticvelocity of acoustic waves in the two outer busbar regions is lower thanthe acoustic velocity in the center region; an acoustic velocity ofacoustic waves in the two inner busbar regions is lower than theacoustic velocity in the center region; an acoustic velocity of acousticwaves in the two coupling regions is higher than the acoustic velocityin the two outer busbar regions or the acoustic velocity in the centerregion; an acoustic velocity of acoustic waves in the two gap regions ishigher than the acoustic velocity in the two inner busbar regions or theacoustic velocity in the center region; and an acoustic velocity ofacoustic waves in the two wide regions is lower than the acousticvelocity in the center region.
 17. The acoustic wave device according toclaim 1, further comprising: a first wiring layer that electricallyconnects the interdigital transducer electrode to the first terminal;and a second wiring layer that electrically connects the interdigitaltransducer electrode to the second terminal.
 18. The acoustic wavedevice according to claim 1, wherein: the piezoelectric body portionincludes a high acoustic velocity support substrate, a low acousticvelocity film is directly laminated on the high acoustic velocitysupport substrate, and an acoustic velocity of bulk waves that propagatethrough the low acoustic velocity film is lower than an acousticvelocity of the acoustic waves that propagate through the piezoelectricbody portion.